What are some safe and free game sites?

Don't let your kids use these sites unless you're supervising them. Miniclips and addictinggames both have some great games for kids, BUT those games are mixed in with games that ARE NOT appropriate for children. By not appropriate, I mean containing language, themes and violence that younger kids (3-12) should not be exposed too. Also many of the ads are for games and game sites that are you don't want a child 12 and under to play.
If your child wants to play games on these sites, only allow them to do so if you're there with them. Make it clear that they are not to click on a game until you've checked it out first.