Sites: Grades 5 – 8

A collection of brain teasers, puzzles, riddles, games and optical illusions.

http://www.brainbashers.com/
Math puzzles and games
http://www.coolmath.com/

Riddles

http://www.figurethis.org/challenges/toc.htm
Riddles, Puzzles
http://www.puzzability.com/puzzles/index.shtml

Math games to Practice Math

http://www.funbrain.com/

Games online to play with! Tangrams

http://pbskids.org/sagwa/games/

Online Games

http://www.counton.org/games/

Math puzzles, Problem of the Week, Library

Challenges

http://mathschallenge.net/index.php?section=problems
http://www.aplusmath.com/Games/index.html 
 
Probability puzzles
     
        
         The Birthday Problem

Practice with Fractions

http://www.visualfractions.com/
http://www.coolmath.com/fractions/index.html
http://www.homeschoolmath.net/math_resources_3.php