Those are some great FFT resources, Rebecca - thanks for sharing! I also wholeheartedly second the recommendation for the DSP Primer book.

In addition, I have linked the following FFT overviews to people who are intimidated by articles that lean towards the more academic end of the spectrum:

1. The DFT "à pied": Mastering the Fourier Transform in on day: http://www.dspdimension.com/admin/dft-a-pied/

(The author of this article acknowledges that it'll take more than one day to truly grok DFT.)

2. Katja's homepage on sinusoids, complex numbers and modulation: http://www.katjaas.nl/home/home.html

(Katja uses wooden anatomical dolls and photos to reinforce the mathematical relationships between complex numbers, sinusoidal waveforms, etc - useful for building up mental models)

Cheers,

Anthony.