http://www.booktalk.org
A freethinkers/atheist/agnostic/whatever book discussion community. Every two months we vote on and choose a book to read and discuss. At the end of the period we often invite the book's author to come and appear in a chat session with us.
There are also other sections of the forum, unrelated to any particular book, where we discuss science, philiosophy, religion, politics and other such topics.