http://treehousetv.com/
They have great games, coloring pages you can print off, there is even a game of the week called mouse control.
My kids use this site sometimes.
http://www.poissonrouge.com/
This is also a good site for the really young ones. They can do several different things.
When you first enter it asks for a purchase or donation, but if you just click on it, it goes away. The school my daughter attends uses this site. And I use it as well.