Dan Barker, former evangelical preacher and now co-president of the Freedom from Religion Foundation. His autobiography is Losing Faith in Faith and he also wrote Godless: How an Evangelical Preacher Became One of America' Leading Atheists.
Bart Ehrman, Biblical scholar who trained to be a pastor and became an atheist. He peeked behind the curtain and found out that the Wizard was a fraud. Most of the video summarizes the main problems in the transmission of the books of the Bible and early debates about Jesus:
Seth Andrews, former Christian broadcaster and now podcaster and speaker, wrote Deconverted: A Journey from Religion to Reason.
Jerry DeWitt, another ex-pastor (Pentecostal), wrote Hope After Faith: An Ex-Pastor's Journey from Belief to Atheism. He is the first graduate of The Clergy Project, started by Dan Barker and Richard Dawkins to give closet atheist pastors a safe place to discuss transitioning to secular life.
Teresa Macbain, also a member of The Clergy Project. She came out despite certain unemployment, and she is now a speaker and Public Relations Director for American Atheists. (Mute until she is at the podium b/c there's terrible feedback):
Matt Dilahunty of The Atheist Experience:
Michael Shermer (blog post): he read up on evolution in order to debunk it, and became a skeptic and atheist
I don't know if this guy is famous but he ought to be! He tried to convert "natives" and they deconverted him:
And the classic, "Why I am Not A Christian" by Bertrand Russell (not read by him):
His answers to lame questions in an interview. His deconversion is part of the interview: