Youngzine has news for kids, and you can create a classroom where you post assignments. There are also games.
MrNussbaum has amazing math games for almost any topic. My kids love the Probability Fair.
Glogster is great, but not really a game. My kids ask to go on during their free choice time, though. I've paid for a classroom account, so I can see what everyone creates. Basically, it's a poster creating site. There are cool backgrounds and stickers to use. Here's a link to one of the Glogs created in my class about the Presidential Primary