Math

http://tabuladigita.com
Online science game for students in grades 3 to 5.  Students create their own avatars to play the the series' four multiplayer games.

http://www.mathplayground.com
Collection of games that include flashcards, memory games and word problems.

http://www.aaamath.com
Access hundreds of pages to enhance math skills with interactive practive for every kind of math problem.

http://www.funbrain.com
Collection of math and reading games, flash arcades for students.

http://www.mathcats.com/storyproblems.html
Math story problems created by kids.  Problems can be completed on-line or printed on worksheets.

http://www.free.ed.gov/resource.cfm?resourceid=1851
Provides interactive on-line math lessons, activities and assessments.

http://www.coolmath.com
Explore a world of math wehre difficult problems can be fun and discover hundreds of resources, exercises, and an amusement park devoted exclusively to math.

http://www.rrojas.com/math.html
Several math practice, lessons and games.

http://www.nlvm.usu.edu/en/nav/vlibrary.html
Manipulatives and concept tutorials for mathematics instruction (K -12) emphasis.