Noticed that the 4 year old Preacher thread blew up today... I didn't really spend much time there, but I figured that I would recommend a couple of books.
"The Varieties of Scientific Experience: A Personal View of the Search for God" and "The Demon-Haunted World: Science as a Candle in the Dark"
Whatever side of the religious argument one is on, these books (especially "The Varieties...") just offer more 'grist for the mill, as it were.
Both are by Carl Sagan, who, in my opinion, is one of the most intelligent, insightful, positive and articulate men that have ever walked this earth. Bit of a personal hero of mine - also check out Cosmos, if you haven't seen it; dated, but still good.