These music sites have interactive music games as well as information about famous composers. Most of these sites center around classical music.
Classics for Kids - WGUC
http://www.classicsforkids.com/
New York Philharmonic Kids Zone
http://www.nyphilkids.org/
Online Music Games
http://www.flashmusicgames.com/
San Francisco Symphony Kids
http://www.sfskids.org/templates/splash.asp
Music Tech Teacher
http://www.musictechteacher.com/musicquizzes.htm
Quizzes and information on music and music theory
Chrome Music Lab
https://musiclab.chromeexperiments.com/
Radio City Music Hall Virtual Tour
http://www.samrohn.com/360-panorama/radio-city-music-hall-360-virtual-tour/