This site has tons of resources. It was created by a teacher and claims to have lesson resources and games from Pre-K through 6th Grade, in Math, Language Arts, History, Geography, and Science. I first came across this site when looking for History and Geography resources.
He has created some original games which are nice. However, some of the games have the same repeated concept that can lose the interest of the kiddos quickly. Also, some of the games do not have the directions written out very clearly which can be frustrating for the first time user.
However, there are tons of games which always is a nice change for kiddos as opposed to worksheets and such. Plus it is free. You can check it out here.