Atheism - Provides proofs that atheism is invalid. Also has tips on how Christians and atheists should communicate. - http://www.carm.org/atheism.htm
Wasteland of Wonders: Atheism - Articles about atheism, humanism, and skepticism. - http://www.abarnett.demon.co.uk/atheism/
Wikipedia: Atheism - Online encyclopedia details the history of atheism, the different types, and how it relates to the religions of the World. - http://en.wikipedia.org/wiki/Atheism
BBC: Atheism - An introduction on the history, rituals, and different types of atheism. - http://www.bbc.co.uk/religion/religions/atheism/
Religious Movements: Atheism - Includes the history, beliefs and sacred texts of atheism. - http://religiousmovements.lib.virginia.edu/nrms/atheism.html
Atheism and Agnosticism - Looks at the similarities and differences between atheism and agnosticism. - http://plato.stanford.edu/entries/atheism-agnosticism/
Dave's Things To Think About - Provides a collection of essays about contemporary theological issues from a sceptical perspective. - http://users.rcn.com/davestul/things.html
Ethical Atheist - Group resisting the influence of religion while promoting a scientific and nonreligious worldview. - http://www.ethicalatheist.com/
Morality Without God - An essay which discusses whether morality is evidence of God. - http://www.spectacle.org/1095/moral.html