Electronic Music Interactive is a multimedia primer for electronic music. Developed by the New Media Center at the University of Oregon, the Shockwave/Flash site provides sounds, diagrams and animations that explain the elements of electronic music.
The site gives vistors an overview of the subject, and demonstrates concepts like the relationship between the shapes of waves and their sound.
It is tough to navigate at first, but once you get the hang of it, it is an excellent way to learn about some of the fundementals of electronic music.