Links:
Eric Weisstein's World of Mathematics - Great encyclopedic knowledge of all things mathematical.
Math Mojo - New site for people to improve their math skills.
Exploremath.com - Cool site with many math tools for educators.
Innumeracy.com - New web site covering various math and logical errors.
About.com - Mathematics - Good general resource with additional monthly articles.
Home page of John Allen Paulos.- Paulos has a new book out called Once Upon a Number
Skeptics Dictionary (or "The Glossary of Scientific Mistakes")
The Most Common Mistakes in Undergraduate Mathematics
Mathmatically Correct - A biased but interesting site on the politics of math education
Sources and Further Reading: (clicking a title will take you to amazon.com)
Dewdney, A. K., 200% of Nothing: An Eye Opening Tour Through the Twists and Turns of Math Abuse and Innumeracy, John Wiley and Sons, New York: 1993.
Paulos, John Allen, Innumeracy: Mathematical Illiteracy and its Consequences, Hill and Wang, New York, 1988.
Paulos, John Allen, A Mathematician Reads the Newspaper, Basic Books, New York, 1995.
Hofstadter, Douglas, Metamagical Themas, Basic Books, New York, 1984.
Capaldi, Nicholas, The Art of Deception: An Introduction to Critical Thinking, Prometheus Books, Buffalo, New York, 1987.