http://mathtest.ccsd.net/ Mathematics Proficiency Practice.

http://www.forum.swarthmore.edu - Collection of math sites.

http://www.actden.com- Math problems online, contests, etc.

http://www.mathcounts.org/gofigure/html/ - Interactive mental math site.

http://euclid.math.fsu.edu/Science/Software.html - a software index of math programs.

http://enc.org/ - Great K-12 math and science resources.

http://www.algebra-online.com/ - Designed to let math buffs talk with each other.

http://www.aimsedu.org/Puzzle/Puzzlelist.html - Math puzzles.

http://www.aplusmath.com- For math worksheets and answers