Co-opoly is a cooperative game that teaches players about how cooperatives work. Players win or lose together. Read more:

ECT.coop » New Game Teaches About Cooperatives.

An innovative social network for children that allows them to tackle humanitarian challenges while earning service credit and winning prizes. Check it out here:

KooDooZ – A social network for kids who want to make a difference!.

Mithril is an MMORPG to teach Math. I just discovered it and it looks really promising. Check it out here:

Mithril – The Epic Math-MMORPG.