Hey Pete,
You mentioned that a lot of people had recommend the God Delusion to you, but I just wanted to mention that if you are interested in atheist thought the more primary sources would be Schopenhauer, Baron d'Holbach, Bertrand Russell, and David Hume. I feel that most of their thoughts have simply been recycled throughout the last century or so. Even Freud had little new to say on the subject. Of course, there is always Epicirus, but his work so fragmentory and outdated that it is sometimes better to go with some post-enlightenment sources. Also, Anthony Flew and Kai Nielsen are particulary well versed amongst contemporary writers. The fact is, little has changed in the debate over the centuries and those like Nielsen and even J.L. Mackie do a much better job incorporating phyiscs and biology when needed. The problem about Dawkins, Harris and a few others amongst the new atheists is that they have changed their methodology on how to express their ideas into a much more combative form, similar to the some of the French intellectuals during the Enlightenment and the late 19th century psychologist/philosophers like Nietzsche and Freud.