Western culture has a tendency to describe unfamiliar things in familiar terms. One of the consequences of this in religion is a variety of entities being equated with Satan even though the native believers might never make such a comparison.
For a discussion on the variety of religions that do explicitly reference Satan, check out "Who is Satan?"
ZoroastrianismZoroastrians acknowledge the existence of a destructive spirit known as Angra Mainyu which westerners often equate with Satan and whose existence may very well have influenced Judeo-Christian views of Satan. Angra Mainyu was created with free will by the one true god, Ahura Mazda, and chose its evil and destructive path. While less than Ahura Mazda, Angra Mainyu is always in conflict with him and humanity, and Zoroastrians struggle to keep his influences at bay here on earth.
The YazidiThe Yazidi honor Melek Tawus, an archangel created by God. Melek Tawus, like the Islamic Iblis, refused to bow to Adam. However, while Muslims revile Iblis for disobeying God, Yazidis honor Melek Tawus for refusing to give Adam honor they feel is only deserved by God.
Because of the similarity between Melek Tawus and Iblis, Muslims often refer to Melek Tawus as a shaitan and to the Yazidi as devil-worshippers. This misunderstanding is often reflected in Western understandings of the Yazidi as well. However, Melek Tawus is not associated with evil or sin. In fact, his tears of repentance extinguished the fires of hell. He is a creator entity who helped to shape the world and humanity, and he is an emanation of God, a reflection of the divine spirit.