AAA Math http://www.aaamath.com/

Brain Teasers http://www.eduplace.com/math/brain/ 

Cool Math http://www.coolmath.com/

Math Cats http://www.mathcats.com/contents.html

Math Dictionary for Kids http://www.amathsdictionaryforkids.com/

Math is Fun http://www.mathisfun.com/

Webmath http://www.webmath.com/index3.html