The Math Forum   A great site to "Ask Dr. Math", try a few interesting problems or find information on mathematical topics.

National Library of Virtual Manipulatives   Interactive site sponsored by the University of Utah.

Math Counts  New Jersey's Math Counts website.
Fun Brain   A collection of math games and educational resources
Figure This   Math Challenges for Families
The ArithmAttack   How many problems can you answer in 60 seconds
A-Plus Math  More math games and puzzles.
Cool Math  Puzzles, Games and Lemonade Stand (Click on Kids)
Quia Math  A collection of games to improve basic skills.
Algebra Help.com   A great site for extra problems, tutorials, and lessons on Algebra
Purplemath.com   Algebra Lessons and tutorials.
Shodor  A host of interactive demonstrations and applications.
Tessellation Lesson