The Dominion is divided between people who think the spirits signalled the birth of the world, and the Faloran influenced peoples who see it more rationally, and the Falorans themselves consider spirits to be like devils and demons.
Then you've obviously got the mono-theistic Sali, the Messianic Catarans, the spirit-worshiping and spirit-consuming Zumai (who actually do see the larger spirits as things to be feared and worshipped, but see them as a part of the jungle, and the smaller ones it's kill or be killed, much like any other beast) the Thac-dur or Yotur (I forget which) who live in peace with their spirits and seek to appease a terrifying sleeping-god under the sea.
The Tenkou Courts see the spirit world as both a mirror to and above the mortal world. They interact with spirits, but there is a strict hierarchy in all aspects of their life, with spirits considered separate and above them. Their culture mirrors the japanese or chinese idea of spirits. No gods to be worshipped, but spirits to ask for assistance, except this time, you ask in the way you might ask someone who is higher in station than you. They are more likely to help because of the idea that the people under them aren't just serving, but they are their responsibility.
Samar are sort of… Native American, I guess. Folk beliefs in spirits as guides and mentors, and the great big (and dead) tree god is a major deity to them. They have a tradition of spirit-quests in the wilderness, coming back with a pacted spirit.