Matan Uberstein: Good post on computeSpectrum function. Also, Matan created a custom SoundSpectrum class you might want to check out.
lab.andre-michelle.com Some great experiments with sound. In particular, check out the Tone Matrix and Karplus-Strong Guitar.
Generating sounds dynamically in Flash Player 10
Good explanation of extends-override-and-super in AS3/
Model-View-Controller AS3 sample (for the programmers out there)