The FFT Demystified (Popularity: )

A web text explaining the techniques of discrete and fast transforms.

Fast Fourier Transforms (Popularity: )

Survey and history of FFT algorithms from Wikipedia.

Mathematics of the Discrete Fourier Transform (DFT) (Popularity: )

Notes by Julius O. Smith III, Stanford.

Introduction to the Fourier Transform (Popularity: )

Notes on applications to Image Processing.

Fast Fourier Transform (Popularity: )

Article in MathWorld.