It's been a while since I've read any of his stuff, but my overall opinion hasn't just emerged from nowhere.
I haven't read Carrie, most likely because I didn't think much of the movie, and although I see where you're coming from with the 'religion can be bad' angle, it's a simple facet of life that there are many degrees between people, and that not all religious people are the archetypal angels they see themselves in the mirror. In fact religion has absolutely nada to do with what makes a person good or bad, so the fact that King uses a religious person to represent badness isn't too much of a stretch of imagination.
Anyway, as for his books, how about The Green Mile or IT, and you also rightly mentioned The Stand, which although I enjoyed at the time, has undeniably religious overtones about it. Generally, his characters all seem to believe in god and this in itself can be irritating when it is mentioned consistantly. I think IT though was the final straw for me, for not only did I find it preachy, but it was also an incredible bore for me.
I could be wrong though, and even if I'm not, I'm sure it won't turn you King fans off one little bit, and that's cool with me too.