James Randi Educational Foundation
The James Randi Educational Foundation is a non-profit learning resource aimed at promoting critical thinking everywhere.

Skeptic Society and Skeptic Magazine
The Skeptics Society is a scientific and educational organization of scholars, scientists, historians, magicians, professors and teachers, and anyone curious about controversial ideas, extraordinary claims, revolutionary ideas, and the promotion of science.

Committee for Skeptical Inquiry
World-wide organization that encourages the critical investigation of paranormal and fringe-science claims from a responsible, scientific point of view.
The Official Richard Dawkins Website.

SkepticWiki is an encyclopedia, written from a sceptical point of view. The site is a wiki, which means that anyone with an account can edit articles, simply by clicking on the edit this page link. It runs on MediaWiki software.

The Secular Web
The Secular Web is the world's most comprehensive website devoted to the promotion and defense of a naturalistic worldview, the view that our natural world is all that there is, a closed system in the sense that nothing that is neither a part nor a product of it can affect it. The Secular Web includes the world's largest library of secularist literature online, and many useful resources for atheists, agnostics, and freethinkers.

Freedom From Religion Foundation
National organization of freethinkers (atheists, agnostics) in Madison, Wisconsin, working to keep state and church separate and to educate the public about the views of nontheists.