There is a clear overlap between the ancient Ugaritic religion and Judaism (and by implication, Christianity and Islam as well). However it seems that such information is hardly known to the average adherents of those religions implicated.
It should be made clear that the information presented is not some minority view or "heretical"/"atheist" propaganda. The data here can be found in archeology books pertaining to ancient middle east religions or, more specifically, the canaanite religion. In fact, some of the sources I'll be citing or quoting from are religious sources.
I first stumbled across this topic when watching the Atheist Experience TV show podcast. Tracie Harris co-hosted 3 episodes (Episodes #464, #466, #483) where the topic was discussed. And here is the relevant blog post on the Atheist Experience blog: Ugarit and the Bible.
If you do a Google search on "Ugarit and the Bible", this webpage by the Quartz Hill School of Theology comes up on top: Ugarit and the Bible. This also one of the sources cited by Tracie Harris at the AETV blog. As far as I can tell, the information on the page is accurate and is comparable to those found in the books at libraries. So this shouldn't strike anyone as being non-mainstream.
I'll let them speak for themselves why Ugaritic text pertains to the bible:
Why should people interested in the Old Testament want to know about this city [Ugarit] and its inhabitants? Simply because when we listen to their voices we hear echoes of the Old Testament itself. Several of the Psalms were simply adapted from Ugaritic sources; the story of the flood has a near mirror image in Ugaritic literature; and the language of the Bible is greatly illuminated by the language of Ugarit.
Let's begin with the word "El". Correction, the name "El". While "El" is translated as a generic word for "god" in the hebrew bible, this was not the case before. According to the ugarit religion, El is a proper name for the supreme deity of the ugaritic pantheon. He is identified as the creator of "the heavens and the earth", the father of 70 gods as well as the father of man.
Elohim is plural. Not singular as advocated by translators of the bible. Elohim refers to El's pantheon of gods, his council.
And Yahweh? He was one of the 70 sons of El. Here's the relevant quote from Wikipedia regarding the development in ancient Israel:
In the earliest stage Yahweh was one of the seventy children of El, each of whom was the patron deity of one of the seventy nations. This is illustrated by the Dead Sea Scrolls and Septuagint texts of Deuteronomy 32:8-9, in which El, as the head of the divine assembly, gives each member of the divine family a nation of his own, "according to the number of the divine sons": Israel is the portion of Yahweh. The later Masoretic text, evidently uncomfortable with the polytheism expressed by the phrase, altered it to "according to the number of the children of Israel"
I know I am quoting Wikipedia, which is not exactly scholarly material, but I'm only doing so because the content agrees with the books I read in the libraries as well as other online sources.
Notice the parallels between El and Yahweh and it becomes obvious the worshipers of Yahweh assimilated the characteristics of El into Yahweh at some point in history. And it seems that theologians know this:
Other deities worshipped at Ugarit were El Shaddai, El Elyon, and El Berith. All of these names are applied to Yahweh by the writers of the Old Testament. What this means is that the Hebrew theologians adopted the titles of the Canaanite gods and attributed them to Yahweh in an effort to eliminate them. If Yahweh is all of these there is no need for the Canaanite gods to exist! This process is known as assimilation.
This assimilation seems to be demonstrated by the association of El's consort (ie, a goddess), Asherah, with Yahweh.
Athirat, or as she is referred to sometimes, Ilat (i.e., goddess of the god El), is the most prominent goddess in the Ugaritic pantheon, though her origin appears to go back well before Ugarit (1200-1400 B.C.E.) to the time of the Ebla tablets. In the Ugaritic pantheon she is the consort of El. She is referred to as the "mother of the gods" or "procreatress of the gods." She thus shares in El's creative work. She is also referred to as "Lady Athirat of the sea" and by the Semitic word qd (i.e., holy). She figures prominently in the Ugaritic texts in which Baal and Anat are requesting from El a palace for Baal to live in (CTA 4), texts concerning Shahar and Shalim (CTA 23) and in another wherein she is said to receive a sheep offered in sacrifice. The name Asherah is the designation often given this goddess in the Old Testament.
Between the eighth to the sixth centuries El became identified with Yahweh, Yahweh-El became the husband of the goddess Asherah, and the other gods and the divine messengers gradually became mere expressions of Yahweh's power.
From the Quartz Hill School of Theology
One of the most interesting of these lesser deities, Asherah, plays a very important role in the Old Testament. There she is called the wife of Baal; but she is also known as the consort of Yahweh! That is, among some Yahwists, Ahserah is Yahweh’s female counterpart!
Apparently it seems that there is also evidence for the assimilation of Baal Hadad into Yahweh. Baal Hadad is a storm god and the only one in the Ugaritic pantheon that is identified by the title "rider of the clouds". This title is later attributed to Yahweh in the bible. For those who wouldn't mind reading longer articles, check out this article on Bible.org: Baalism in Canaanite Religion and Its Relation to Selected Old Testament Texts [Google Cache version].
For those want to read more, check out Wikipedia on these topic as well. See "Canaanite religion" and "Early history of Yahweh worship".
The relationship between Yahweh of the Abrahamic religions and the gods of the Ugaritic pantheon (in particular, El) is obvious.
Why isn't this information more widely known?
More unusually, why don't such knowledge pose a problem to adherents of those faiths? I would think this would make it more than obvious that religions are made up (ie, fiction).
What's your excuse?
Update (2 Dec 2011): Evid3nc3 has an excellent video about evolution of monotheism from polytheism based on Karen Armstrong book, A History of God. It includes how Yahweh became the "One God".