Texas Instruments
Texas Instruments: Fourier Analysis
Students use the TI InterActive! software to explore the connection between a function and its Fourier series.
Wikimedia
Wikipedia: Simple Harmonic Motion
Wikipedia offers great information on simple harmonic motion, including an image, formulas, and hyperlinked terms.
Other
Physics and Psychophysics of Music
This site is filled with information pertaining to the physics of sound and music.