allmath.com- cool site with math flashcards, multiplication tables, biographies of mathematicians, and a glossary of math terms.
Mathematics with Alice - takes you on a course through Mathematics with the help of Alice, the girl in Lewis Carroll's stories. Includes a biography of Carroll as well as math tips and problems.
Basic Facts Practice - Flashcards for home schoolers or homework
APlusMath - More Flashcard
BoxerMath.com - Little more advanced.