One of the recommended lectures on a logic class I had at my school, which was run by missionary nuns from Minnessota (and the teacher himself was catholic), was Carl Sagan's The demon-haunted world. It turned me into an atheist.
Yes, In a lot of ways Sagan was a forerunner of the "New Atheists" like Dawkins and Dennet, but I think The Demon-Haunted World was more effective because it didn't go the confrontational "religion is evil" route rather than just gently point out the flaws in the religious world view and so could actually convince some people who weren't already atheists.
