Music Tech Teacher: http://www.musictechteacher.com/musicquizzes.htm

Teoria: http://www.teoria.com/

DSO Kids: http://www.dsokids.com

Classics for Kids: http://www.classicsforkids.com/games/

Creating Music: http://www.creatingmusic.com/

Music Express: http://www.musicexpressmagazine.com/kidscorner/index.jsp

Music Training Games: http://trainer.thetamusic.com/en/content/music-training-games