The Dallas Symphony Orchestra Kids
This educational site contains games, activities, a listening lab, and many more fun and exciting sections all about music!

The New York Philharmonic Kidzone 
This educational site consists of several sections that teach all aspects of music including composers, instruments, games, and even a composition workshop.

The San Francisco Symphony Kids
This website, in conjunction with the live performances of the San Francisco Symphony, provides a great way for people of all ages to hear, learn, and have fun with music.

8notes
This site is great for finding music specific for your instrument, learning about composers and styles of music, as well as some interactive theory lessons.  It even contains a metronome and a place to generate your own blank sheet music to begin your very own composition!

Music Theory
This site has exercises to help with note names and values.  You can even customize your own lessons.

Metronome Online
This is an online metronome ideal for quick and easy use while practicing music.  This music tool helps with your rhythm as well as tempo selections and it is always available for free to all students of music!

Phil Tulga - Music Through The Curriculum
This site contains a large number of free music activities and arts integrations lessons that connect music to reading, math, and science.  Many useful activities are located here, especially the counting music feature that counts out any rhythm you create!

Blank Sheet Music
This site is great for students who want to write their own compositions.  Choose from several options and then make your own kind of music!

Noteflight
Noteflight is an online music writing application that lets you create, view, print and hear music notation with professional quality.  Basic accounts are free so be creative!

Music Scores
This site contains sheet music and arrangements for each specific instrument!  Over 290 files are free to download and enjoy.

"Musical compositions, it should be remembered, do not inhabit certain countries, certain museums, like paintings and statues.  The Mozart Quintet is not shut up in Salzburg:  I have it in my pocket."  ~ Henri Rabaud