Check out these great websites:
Music Theory and Ear Training:
http://www.musictheory.net
http://www.easymusictheory.com/lessons.html
Metronome:
http://a.bestmetronome.com/
http://bestmetronome.com/
http://www.metronomeonline.com/
Free sheet music:
http://www.8notes.com/
http://www.onlinesheetmusic.com/more-instruments-c1.aspx
http://www.makingmusicfun.net/htm/printit_free_printable_sheet_music_index.htm
http://www.onlinesheetmusic.com/more-instruments-c1.aspx
Composing Music:
http://musescore.org
Various Information and Games:
http://kids.usa.gov/teens/music/index.shtml
http://www.classicsforkids.com
http://www.makingmusicfun.net
Music Theory and Ear Training:
http://www.musictheory.net
http://www.easymusictheory.com/lessons.html
Metronome:
http://a.bestmetronome.com/
http://bestmetronome.com/
http://www.metronomeonline.com/
Free sheet music:
http://www.8notes.com/
http://www.onlinesheetmusic.com/more-instruments-c1.aspx
http://www.makingmusicfun.net/htm/printit_free_printable_sheet_music_index.htm
http://www.onlinesheetmusic.com/more-instruments-c1.aspx
Composing Music:
http://musescore.org
Various Information and Games:
http://kids.usa.gov/teens/music/index.shtml
http://www.classicsforkids.com
http://www.makingmusicfun.net
GAMES