Transform Calculus

Fast Fourier Transform - Article in MathWorld.
mathworld.wolfram.com/FastFourierTransform.html

Fast Fourier Transforms - Survey and history of FFT algorithms from Wikipedia.
en.wikipedia.org/wiki/Fast_Fourier_transform

An Introduction to Fourier Theory - A mathematically inclined introduction with illustrations and explanations of related theorems, its properties and numerical methods for calculating transforms.
gershwin.ens.fr/vdaniel/Doc-Locale/Cours-Mirrored/Maths-Stuff/fourier/

Introduction To Fourier Transform - A description of the principle of fourier transform and subsequent derivation of formulae. Page includes graphs.
www.rnowik.com/document.php=3fid=3d7

Introduction to the Fourier Transform - Notes on applications to Image Processing.
www.cs.unm.edu/~brayer/vision/fourier.html

Mathematics of the Discrete Fourier Transform (DFT) - Notes by Julius O. Smith III, Stanford.
ccrma-www.stanford.edu/~jos/r320/