CMU is looking for teachers to partner with for research on educational games. Read more about the ENGAGE project here and sign up.
Try the games (I have to say I did not play these games because they require a download of a Unity web player and I was too lazy to do it!)
Play RumbleBlocks! at rumbleblocks.etc.cmu.edu
Play Beanstalk! at beanstalk.etc.cmu.edu