Other
Morton Subotnick's Creating Music
This site is an effective and fun way to help children understand music better. There are several online interactive games to play to better understand rhythm, pitch, scales and much more.
University of California
Ucla: Popular American Music
See images and find out about the original sheet music from the early 1900's. Famous songs such as "Dapper Dan", "Down the River", and more. You can search for music by title or author.