There's certainly evidence in the archeological record that early Israelites worshipped more gods than just Yahweh. There was a female deity called Asherah who may have been the wife of Yahweh. And I think Baal is mentioned a few times in the bible as well. Certainly, it talks about jealousy over the fact that Solomon's wives were worshipping foreign gods.

It's not a surprise, really, to see shades of polytheism in the OT biblical texts. They were first put to print, so far as is known, around the 7th century BC, right during the Greek classical age. And who knows how long Hebrew religion was reliant on oral tradition before that...

In fact, there is a direct parallel between Greek and Hebrew myth in the book of Isaiah. The passage 45:7 states "I form the light, and create darkness: I make peace, and create evil: I the LORD do all these things." This lines up with a certain understanding of Zeus in that Greeks believed he had two jars at his feet, one of good and one of evil, and from each he gave a portion to each person upon birth.

Plus, it's no coincidence that the Hebrew underworld - Sheol - has more in common with Hades than Hell and that the Devil/Satan doesn't show up as a villain until much later in the bible. Read closely and you'll find that the earliest mention of Satan in the OT has him on the side of Yahweh.

I don't know if you can still find it, but there's a decent BBC film called Andy Hamilton's Search for Satan that gives some good information. And Terry Jones of Monty Python fame one did a film called The Surprising History of Sex and Love that offers more information in this area. Also look for a BBC film by Aleister Sooke called How the Devil Got His Horns.