FunBrain is the #1 site for online educational games for kids of all ages. (math, grammar, science, spelling, history) Click on your grade. Choose a subject link a variety of games and activities.
Find help for homework and find links to variety of subjects and games.
http://nobelprize.org/educational_games/
These games and simulations, based on Nobel Prize-awarded achievements, will teach and inspire you while you're having FUN!
http://pbskids.org/
Links to videos and games with popular PBS show themes characters.
http://www.arcademicskillbuilders.com/
Math and language arts games that engage, motivate, and help teach. Click a button and play multi-player or single-player games!
http://www.sheppardsoftware.com
Games that will exercise players' brains. USA, World, Animals, Vocabulary, Health, Science, Math, History, Brain, etc.
http://quizhub.com
The Fun K-12 Online Interactive Learning Center.