I have a couple posts in the works, but thought I should direct people to this post instead on the Sword of Mass Destruction blog.
Sword of Mass Destruction: Rethinking clerics and religion, part 1
There are some points where I might disagree, but that's mostly because I think of religion in terms of structural anthropology and Indo-European studies (Georges Dumézil and the like.) It's not relevant to the topic, which is how to design religions for your D&D game. Of course, rather than going through a checklist like this, my approach would be more like "take two or three actual historical cults and merge them, change the names, and add a little spice to make it feel unique." But you still need to keep things like this in mind when looking for cults to borrow.