The Oberlin College Conservatory of Music, founded in 1865, is the nation's oldest continuously operating conservatory, and the only major music school in the country linked with a preeminent liberal arts college.

Essentials of Music -  A super resource for classical music lovers.  Contains on-line references to the six main eras of music, over 70 famous composers,  and a glossary of musical terms. Sponsored by Sony's Classical and W.W. Norton

Playmusic.org - This is an interactive guide through the orchestra designed for kids.  Sponsored by the American Symphony Orchestra Leauge.
American Symphony Orchestra League - The American Symphony Orchestra League provides leadership and service to American orchestras while communicating to the public the value and importance of orchestras and the music they perform.
Classics for Kids® is here to help you learn about classical music and have fun too! From Cinncinatti Classical Public Radio

Carnegie Hall Listening Adventures - Great performances of classical music with interactive listening guides and notes.
Dallas Symphony Orchestra Kids - Interactive games plus information on instruments, composers and classical music in general.