M&R Kid's Games
http://math-and-reading-help-for-kids.org/

Level 1 (continues on to Level 2 and 3)
http://www.oswego.org/

Invention Playhouse
http://www.inventionatplay.org/

Math TV
http://www.actionmath.com/

Online Sudoku
http://www.counton.org/sudoku/

Cool Math 4 Kids
http://www.coolmath-games.com/

Interactive Mathematics
http://nlvm.usu.edu/

Games Wheel
http://www.bbc.co.uk/

Enchanted Mind
http://www.enchantedmind.com/

How's Your Short Term Memory?
http://faculty.washington.edu/chudler/stm0.html

Memory Notes
http://www.uen.org/7-12interactives/brain.shtml