If you enjoyed Jesus Camp, I also recommend Hell House. It's a documentary about a church that puts on a Haunted House, with the goal of showing the visitors a little bit of hell in the world. The goal being that they can then share the gospel of Jesus with the visitors, which would save them from hell.
I thought both Jesus Camp, and Hell House do a great job of showing what is going on with the groups, and letting the viewer make up their own mind. At the least it stirs up conversation.
Lake of Fire, is another documentary that I'm looking forward to, that deals with the abortion debate in America.