Michael J. Totten has an interesting piece where he interviews the religious leader of the Yezidis. I read a book on the Yezidis in college…and their “history” is difficult to untangle. If I had to bet I would contend that their assertion of the being the ur-religion of the Kurds is a rather late invention. I once talked a Kurdish cab-driver in Chicago who repeated the idea that Yezidism was the Kurdish ur-religion, so this idea seems accepted among Muslims. The Yezidi beliefs are a melange, and there are indications from their rituals that they were either Jacobite Christians or strongly influenced by Jacobite Christianity. Additionally, there are historical records of paganism within the mountains of Kurdistan, during the 17th century a Ottoman padishah was making his progress through this region and stumbled upon a village where everyone worshipped the sun. This solar paganism offended the padishah, and eventually the village converted to Jacobite Christianity (at least outwardly) to avoid his wrath. This area has a long historical record of solar paganism, the city of Haran in upper Syria was spared forced Christianization1 during the 6th century because of special protection that the Persian shah extended to it (though it was in Byzantine territory, its nearness to the Persian Empire rendered it vulnerable to attack). Haran remained a pagan city with an indigenous religion at the time of the Muslim conquest.
The Middle East certainly has many peculiar cults. One observation I have read is that the closer you get to the center of the Islamic world the greater the variation in belief and tendency toward heterodoxy. For example, the frequency of Shiism drops to zero at the antipodes of the Dar-al-Islam. The Muslim nations with non-Sunni majorities or large minorites are generally part of the “Islamic core,” many of the Gulf states (including Saudi Arabia), Oman, Yemen, Syria, Iran and Lebanon. Heterodox semi and quasi Islamic groups also seem far more prominent in the Fertile Crescent than elsewhere. Aside from the Yezidis you have the Druze, the Alevis, the Alawites and the Mandaeans.
1 – The Baalbek valley was forcibly Christianized while missionaris were sent into central Anatolia during the 6th century under Justinian so as to finally complete the nominal unification of the Byzantine Empire religiously.