Source Code in Fortran for FFT from "Programs for Digital Signal Processing", 1979, IEEE Press, ISBN 0-87942-127-4. The book is necessary to use and understand these source code listings.

Benchmark comparing speeds of many FFT codes. Results from many machines, and code to run it yourself.

Contains Fast Fourier Transform source code (C, C++, Pascal), tutorial, and math theory.

Links to many sources of FFT code and information.

Links and various Fortran FFT implementations.

A package of Fortran subprograms for the fast Fourier transform of periodic and other symmetric sequences.

Fast free C FFT library; includes multi-dimensional, real-complex, and parallel transforms.

Arbitrary length FFT C-source, 3D gravity simulator, quantization of FIR filter coefficients. C source.

Source code and links for many different FFT implementations and related information.

Power-of-two real and complex FFT software that is faster, and more accurate, than conventional iterative implementation of one-dimensional FFTs. Based on a propietary algorithm.

A real-time spectral analysis application with spectral analysis tools, statistical functions and visualization system. It can analyse data from WAV files or sound input from microphone or CD player. Shareware.