How many Judaisms are there? Certainly not nearly as many as there are Christian denominations… but Judaism is anything but monolithic. The present author will lay out in order the various sects of Judaism as they have come onto the scene, with brief descriptions and approximate “birth years” (but bear in mind that sects tend to develop over time rather than emerge in a day).
Edenism (traditionally ca. 3760 BCE or 4004 BCE)
In advance of any of the Judaisms was the Edenic faith — the first monotheistic worship of HaShem. Depending on whose chronology is followed, a start date for this faith could range from 3760 BCE at the more recent end of the span (traditional Jewish chronology), and as far back as 10,000-12,000 years in the “older earth” (selective genealogies) camp. The date of 4004 BCE comes from Bishop Ussher’s chronology (which differs from the traditional Jewish by 244 years).
Deluvian Age Monotheism (probably in continuity with Edenic faith)
We know that Noach was deemed “righteous” in Genesis 6, and this assessment would have been predicated upon his faith in HaShem, as demonstrated by his obedience to his calling to build the ark and preach to the people about the impending judgment. It can be surmised from the small number of people on the ark (only eight) that this was not a popular faith, but there is likely an unbroken line of faith from Adam to Noach. This may be considered a carrying forward of the Edenism already discussed. The date of the Deluge/Flood is traditionally fixed to about 2348 BCE, but Noach’s faith obviously predated this by at least a century, as he was obediently constructing the ark for 120 years (Genesis 6:3). 
Avraham’s Hebraic (Pre-Jewish) Monotheism (ca. 1840 BCE or ca. 2085 BCE)
Ussher has Avraham’s lifespan going from 2166 to 1991 BCE , but traditional Judaism places him at 1948 BCE . Avraham’s break from the polytheism of his father Terah is traditionally considered the foundational start-point for the development of what we now call Judaism. It is with him (and his covenant progeny) that the Everlasting Covenant is forged (Genesis 17:7ff), and that covenant defines Judaism as a structured halakhic system.
Sinaitic Judaism (1446-1406 BCE or 1270-1230 BCE)
The beginnings of a less-than-monolithic Judaism can perhaps be seen in the desert sojournings of Israel. There is a mixed multitude coming out of Egypt — not just Jews. The text of Numbers 10-20 suggests that there were varying degrees of commitment to Israel’s covenantal community within this group. What would later become classifications of “G-d fearer,” “proselyte,” and “ethnic Jew” may find their prototypes in the Arabian desert.
Proselytes (uncertain dating)
This category may actually predate Moshe. There is debate over how to interpret a particular phrase in Genesis 12:5, i.e. “וְאֶת־הַנֶּ֖פֶשׁ אֲשֶׁר־עָשׂ֣וּ בְחָרָ֑ן” (lit. “and the soul which he made in Haran”). Nephesh (נֶּפֶשׁ) is generally treated as a collective noun in this passage (i.e. translated as a plural) either as “souls” (e.g. Jubilee Bible 2000, ASV, DLT, WEB, KJV, et al.) or “people” (e.g. NASB, CJB, HCSB, NIV, NLT, ESV, et al.). ISV translates it as a plural as well, but as “servants.” The debate is over whether the “souls” are servants or converts to the faith… or perhaps both. If proselytes are not to be seen this early, we, at latest, see this in those non-Jews who underwent circumcision in order to participate in Passover (Exodus 12:48). At some point, a conversion formula was instituted consisting of four elements: (1) minchah — offering a sacrifice to HaShem, (2) shomer Torah — embracing and keeping Torah and Tradition, (3) miqveh — a water-immersion (symbolically renouncing paganism), and (4) b’rit-milah — circumcision (sign of the Covenant community). 
G-d Fearers/Sebomenoi/Phoboumenoi (ca. 1446 BCE)
Exodus 12:49 introduces the phrase “the foreigner among you.” These are non-Jews who come under the conditions and stipulations of covenant community by choice, leaving idolatry but retaining their Gentile identity, called in Greek sebomenoi or phoboumenoi.  They find mention in the Apostolic Testament (B’rit Chadashah) at Acts: 10: 2, 22, 35; 13:16, 26 using the term phoboumenos/oi and at Acts 13:43, 50; 16:14; 17:4, 17; 18:7 with the term sobomenos/oi — eleven references in total. Archaeological inscriptions referring to G-d Fearers support their continued existence beyond the Biblical era. 
Pharisees (2nd Century BCE)
They arose in opposition to the Hasmonean Dynasty, in which Judahite Hasmoneans wrested control of the priesthood contra-Torah. The Pharisees did not give themselves the name they bear, which means “separated ones,” but rather were given it as a derogatory slur by the Sadducees.  This sect’s halakhic influence never really waned, as they continued as recorders of the Oral Torah (Talmud, Targumim, etc.) and even today, all rabbinical Judaism now in practice can still be said to be Pharisaic.
Sadducees/Boethusians (2nd Century BCE)
The Sadducees arose in protest to the Pharisees, who originally upheld rulings of the Maccabees.  Graetz’s assumption that the Sadducees were the political opponents and the Boethusians the religious opponents of the Pharisees is tenuous. The Talmud uses these two terms interchangeably, thus it seems that they both refer to the same sect of Judaism, and claiming descent from Zadok. The namesake of this sect is Cohen haGadol Boethus of Alexandria, named High Priest by Herod the Great in 24 or 25 BCE. 
Essenes (2nd or 3rd Century BCE)
The Essenes (אִסִּיִים) were a multifaceted group, ranging from the celibate sect of Qumran called by modern scholars the Yachad (reportedly encountered by Josephus) to the more normative sects known to Philo. Like the Sadducees, they claimed descent from Zadok.  This sect had died out by the close of the 1st Century CE. Around 1900, however, Grace Brown Mann founded the Neo-Essene movement, originally called The Order of the Essenes, though later including the Rosicrucians.
Damascus Covenant Community (ca. 150 BCE)
There were actually two communities at Qumran. The Yachad (keepers of the Dead Sea Scrolls) were decidedly Essene, but there was also a dramatically different sect there which was not celibate and not as rancorous toward Jerusalem who were defined by the Damascus Covenant (4Q271D).
Therapeutae (1st Century CE)
This ascetic sect settled on the shores of Lake Mareotis in the vicinity of Alexandria, Egypt. Little is known about them beyond what is reported in Philo’s De Vita Contemplativa. Per this document, they prayed twice every day, at dawn and at evening, the interval between being spent entirely on spiritual exercise. They read the Holy Scriptures, from which they sought wisdom by treating them as allegorical, believing that the words of the literal text were symbols of something hidden. They dined only at night, after evening prayers.
Messianic Judaism (27 CE)
Messianic Judaism is what Yeshua and His initial followers practiced. It was called by the Pharisees “a sect” of Judaism (Acts 24:5, 14), indicating that they saw it as separate from their own yet still a valid Judaism. First Century Messianic Judaism held much more in common with Pharisaism than with any other sect extant at that time. The apparent conflicts between the two sects can be attributed to “nearest other syndrome,” i.e. the phenomenon that one will clash most often with that entity with which one shares the most in common due to frequency of interaction. Biblical Messianic Judaism is Torah-observant (because Yeshua and the Talmidim were), Gentile-inclusive (based on Psalm 117 and the ministry of Sha’ul), and Israel-centric (as Yeshua commanded it to be). This means that certain theologies are to be deprecated, e.g. Two-House, Two-Path (Antinomianism, Bi-Lateral Ecclesiology), Supersessionism (replacement theology), Dispensationalism (separation theology), Sacred Name cult, Karaism, etc. (these falling more into the Christian Hebrew Roots camp than into Biblical Messianic Judaism). By about 45 CE, Messianic Judaism had spread as far as India (Thomas & Bartholomew carried an Aramaic copy of Matthew’s Gospel there), and by the 2nd Century was carried throughout Asia (including China), Africa, and throughout the known world.  Though this sect was largely absorbed into mainstream “church” by the close of the 4th Century CE, its tenets continued in the hearts of a Believing Remnant of every generation until the culture was such that it could reemerge as an End-time move of HaShem in the late 19th Century. In 1925, the first independent Messianic congregation of modern times was established.
Sicarii/Zealots (founded in late 1st Century CE, after 70 CE)
Sicarii and Zealots may or may not be the same group, but if they were ontologically separate, they are both defined by the same aims. Followers were considered assassins or “dagger-men” (as the meaning of Sicarii suggests). Their goal was to expel the Roman authorities by any means necessary, much as the Maccabees had done a few centuries earlier. 
Karaism (founded in 8th Century CE)
Karaite Judaism was founded by Anan ben David in Persia. The name “Karaite” come from the Hebrew word qara (to read), as this sect believed that a literal reading of the text was preferred over a spiritualized understanding. This sect, like the Sadducees, rejected all extra Tanakhical writings of Judaism, e.g. the Talmuds and Midrashic literature, perceiving them as unauthoritative. They claim to be “the original Judaism which has existed throughout history under various names incl. Righteous, Sadducees, Boethusians, Ananites and Karaites, all of whom obeyed the Torah with no additions.”  There is a Neo-Karaite movement in vogue today, but it is not the same as historical Karaitism; it is a Church-directed Sadducee-ish Hebrew Roots gimmick associated with Michael Rood and Apostle Bailey.
Chasidism/Haredi Judaism (founded in 1734)
The name Chasidim means “pious ones.” Chasidism is the invention of founding rabbi Yisroel ben Eliezer, more commonly known as Baal Shem Tov (1698-1760), but is built largely on the medieval gnostic teachings of Kabbalah mysticism (which most Jewish sects consider nonsense), including those of false messiahs Sabbatai Zevi (1626–1676) and Jacob Frank (1726–1791). Its focus is on the attainment of secret knowledge through “Bible Code” type approaches to Scripture. In the 19th Century, a stream of Lubavitcher Chasidism called the Haredi, which rejects modern secular culture, emerged under this umbrella. 
Reform Judaism (founded 17 July 1810)
An article in the “Jewish Virtual Library” observes, “Early Reform Judaism was also antiZionist, believing the Diaspora was necessary for Jews to be ‘light unto the nations.'”  Modern Reform Judaism (est. 1937) has reversed on some key planks, including Zionism, now emphasizing “the obligation of all Jewry to aid in building a Jewish homeland….” (ibid.) The first Reform movement temple was founded and led by Israel Jacobson (1768-1828). 
Orthodox Judaism (founded 1851 CE)
Originally called “Torah im Derekh Eretz,” Orthodox Judaism was founded by Samson Raphael Hirsch (1808 – 1888, Germany)  and Moses Sofer (1762 – 1839, Hungary) as a reaction against to the liberal sway of Reform Judaism. They also opposed the “historical approach” of Frankel’s movement (see next listing).  Of the modern Judaisms, this one upholds the strictest adherence to the ancient traditions. Orthodox Judaism claims to be the faithful heir to classical, or normative, rabbinic Judaism. 
Conservative/Masorti Judaism (1850s)
Ashkenazi Rabbi Zecharias Frankel (1801 – 1875) was the founder of what began as “moderate middle Judaism” as a reaction against both Orthodox and Reform Judaism. He communicated his message chiefly through the journal he founded: Zeitschrift für die Religiösen Interessen des Judentums. Conservative or Masorti Judaism was originally described as “Positive-Historical Judaism.” The term “conservative” was used with the meaning that Jews ought to “conserve Jewish tradition” rather than to reform or abandon it.  Masorti.org describes the movement this way:
“The Masorti Movement is committed to a pluralistic, egalitarian, and democratic vision of Zionism. Masorti represents a “third” way. Not secular Judaism. Not ultra-Orthodoxy. But a Jewish life that integrates secular beliefs. Halakhah with inclusion and egalitarianism. Tradition that recognizes the realities of today’s world.” 
Reconstructionist Judaism (late 1920s)
Rabbi Mordecai Menahem Kaplan (1881–1983), author of Judaism as a Civilization: Toward a Reconstruction of American Jewish Life, and his son-in-law Rabbi Ira Eisenstein (1906–2001) founded this progressivist, liberal brand of American Judaism as a branch of Conservative Judaism, initially. It takes a more philosophical (Westernized) approach to the Scriptures and the concepts derived from them than the other sects. “Reconstructionists see Jewish tradition, culture, and religion as having grown ‘from the ground up’ instead of from the ‘[mountain-]top down.'”  Reconstructionists diverge from Scripture in that they do not understand HaShem as choosing Israel from among other nations or initiating the Covenant. They believe (more humanistically) that it is the Jewish people who created the Covenant and chose to live within it. 
Humanistic Judaism (1963)
Rabbi Sherwin T. Wine founded this American “non-theistic Judaism” which defines Judaism as the cultural and historical experience of the Jewish people rather than as a religion. Most Jews would not consider this “secular Judaism” as a legitimate Judaism. The Society for Humanistic Judaism explains this aberrant form thus:
“Humanistic Judaism embraces a human-centered philosophy that combines rational thinking with a deep connection to the Jewish people and its culture. Humanistic Jews value their Jewish identity and the aspects of Judaism that offer a genuine expression of their contemporary way of life. Humanistic Jews celebrate Jewish holidays and life cycle events (such as weddings and bar and bat mitzvah) with inspirational ceremonies that draw upon but go beyond traditional symbols and liturgy.” 
Notes & References
- Though some have interpreted the 120 years of this passage to be setting the new “maximum lifespan” for human beings, this cannot be correct. Several Biblical figures live longer than this after the Deluge, e.g. Noach (another 350 years after the Flood for a total of 950 years per Genesis 9:28-29), every generation listed in Genesis 11 from Shem (600 per Genesis 11:11) to Terach (205 per Genesis 11:32), Sarai (127 per Genesis 23:1), Avraham (175 per Genesis 25:7), Ishmael (137 per Genesis 25:17), Yitzchak (180 per Genesis 35:29), Ya’akov (147 per Genesis 47:28), et al. A better reading is to understand the passage as a countdown to the Deluge, i.e. 120 years to destruction.
- John H. Walton, Chronological and Background Charts of the Old Testament (Grand Rapids, Mich.: Zondervan, 1994; orig. 1978), 15.
- Discussion on this dating can be found at http://judaism.stackexchange.com/questions/37236/creation-of-state-of-israel-and-birth-of-abraham-1948.
- John Dressel, Course notes from A Timeline Foundational Study of Messianic Judaism (unpublished; course taught at Adat Eytz Chayim, Comstock Park, Mich., Oct. 2013), 20.
- K. G. Kuhn and H. Stegemann, “Proselyten,” RE, suppl. ix (1962), 1260.
- Scott McKnight, “Proselytism and Godfearers,” Dictionary of New Testament Background (Craig A. Evans, Stanley E. Porter Jr., eds.; Downers Grove, Ill.: IVP Academic, 2001): 840–47.
- Talmud Babli, Tractate Yadayim 4.6ff.
- Alfred Edersheim, The Life and Times of Jesus the Messiah (Peabody, Mass.: Hendrickson, 2004; orig. 1883), 67.
- Josephus, “Antiquitates”, xv. 9, § 3; xix. 6, § 2.
- F. F. Bruce, Second Thoughts on the Dead Sea Scrolls (Paternoster Press, 1956).
- Merchant Prince Shattan, Manimekalai, Gatha 27.
- http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Sicarii.html; http://www.jewishvirtuallibrary.org/jsource/judaica/ejud_0002_0021_0_21428.html
- Lawrence A. Englander, “History of Reform Judaism and a Look Ahead: In Search of Belonging,” Reform Judaism Magazine (online: http://www.reformjudaism.org/history-reform-judaism-and-look-ahead-search-belonging).
- Gerhard Falk, “Origins of Conservative Judaism,” jbuff.com: Jewish Buffalo on the Web (online: http://jbuff.com/c051310.htm)
- Lisa Katz, “Reconstructionist Judaism,” Branches of Judaism (online: http://judaism.about.com/od/reconstructionistjudaism/a/reconstruct.htm)