Smithsonian Institution
Nm Af A: Audible Artworks: Selected African Musical Instruments
Five traditional African musical instruments are highlighted at this Smithsonian site: two types of drums, the thumb piano (mucapata), harp, and whistles. Includes historical facts about the instruments.
BBC
Bbc: Bitesize: Music of Africa
This site is a part of the About Music site of the BBC, and this interactive site lets you explore various parts of Africa, their music, their instruments, their sounds. Requires Real Player.