Yucky.com
http://kids.discovery.com/fansites/grossology/games/game.html
kids.discovery.com/games/whizzball/whizzball.html
(thinking puzzle type game, awesome) Build a better moustrap thing.
THere are also games listed from a-z
http://kids.discovery.com/games/games.html
Puzzles, quizs, games, videos. There is a lot to do for kids on this site.
Antonio