This is the best place on the web to play competitive games. Personally, I love the Pyramid solitaire game, but I'm not much good at it. You can play for money or for free, surprisingly addictive!
Free maths games for older kids, and for adults who want to study mathematics painlessly. The games are surprisingly playable and I especially like Pyramid Panic. These games look like the kind of games you see on Miniclip for instance.