The Secular Web
 World's largest online library of writings and resources in defense of the secular and naturalist worldview.

Center for Naturalism
 Growing library of essays & links that help illuminate and explain the naturalist worldview and its moral & social consequences.

CSI (formerly CSICOP)
 The Committee for Skeptical Inquiry investigates claims that challenge the naturalist worldview.

Apex Naturalism
 Online magazine for philosophical naturalists, featuring articles, news, videos and more.

Worldview Web
 Brief answers to questions from a Christian, Muslim, Hindu and Atheist perspective. I'm the Atheist, and answer as a Naturalist.

Naturalism Facebook
 Facebook resource page on naturalism. Links to websites on practical naturalism.

Stanford Naturalism
 The Stanford Encyclopedia of Philosophy entry on Naturalism (by David Papineau).

Stanford Physicalism
 The Stanford Encyclopedia of Philosophy entry on Physicalism, with extensive ultra-technical discussion of the problems and debates.

Naturalism in the IEP
 The Internet Encyclopedia of Philosophy entry on Naturalism, brief but peer-reviewed, with bibliography.

Varieties of Naturalism
 Philosopher John Shook's analysis of what naturalism is and its different kinds.

Wikipedia on Naturalism
 Wikipedia discussion of definition, history & major arguments for and against metaphysical naturalism.

SkeptDic on Naturalism
 The Skeptic's Dictionary entry on naturalism, with discussion and links.

Courtesy of Richard Carrier