http://www.mathplayground.com/ - contains math games and problem solving games for grades 2-8
http://www.funbrain.com/kidscenter.html - contains links to a variety of math and reading games for grades K-8
http://www.gamequarium.com/problemsolving.html - contains problem solving games
http://www.mhschool.com/math/mathconnects/index.html - links to the school's Math Connects textbook for each grade; contains online tools, activities, and more
http://teacher.scholastic.com/maven/ - Math Maven's Mysteries - you have to use math to solve the mysteries
http://studyjams.scholastic.com/studyjams/jams/math/index.htm - contains step-by-step audio/video directions for solving problems, as well as sample math problems
http://www.onlinemathlearning.com/index.html - provides math assistance for all math topics; for grades PreK-12
http://pbskids.org/lab - NEW!!! PBS KIDS has launched a new site that includes games hosted by favorite characters with the goal of building upon and imporoving math skills
