Guest suggestion - Dean Edell
He has a call-in medical show, and is the author of a lot of books. He never really comes out and says he's athiest, but he pokes fun at the stupidity of theists (christian scientists not getting immunizations is causing an outbreak of measles, guy dies in lions den saying god will save him, etc.) on almost every show.
"Religion is like a badly written contract - most people don't read most (much less all) of it, believe what the other party says, and execute with the best of intentions and naivety."