Here is a list of online musical activities for kids of all ages:

http://www.musictheory.net/

This site is a great tool for music theory, note reading, aural skills, and so on. Use the "settings" selection in "note trainer" to choose the notes you want to drill.

http://www.creatingmusic.com/

Creatingmusic.com is a children's online creative music environment for children of all ages. It's a place for kids to compose music, play with musical performance, music games and music puzzles. Come discover fun and easy ways to make music!

http://www.bbc.co.uk/radio3/makingtracks/games.shtml

Why not use one of the first 4 games to make a tune and send it to Making Tracks? You'll need Shockwave.

http://www.interactiveclassics.com/play_musicgames.htm

Best music games in the known universe! PC Games for Music Lovers Featuring the world’s most beautiful music with thrilling games, colourful characters and wonderful animation.

http://www.gamequarium.com/makemusic.html

Wooden Xylophone, Wubbles Sound Game, Boomthang, Calliou’s Magic Keyboard, Virtual Reality Piano, and more.

http://www.dsokids.com/2001/rooms/DSO_Intro.html

The Dallas Symphony Orchestra's magical doorway to a world of musical fun and learning for students, parents and teachers!

http://www.metronimo.com/fr/jeux/

76 jeux où vous devez reconnaître des musiques au format Real audio, répondre à des questions sur les chanteurs, les compositeurs, les instruments, les notes de musiques...