Joerg's FXT Page  
   Source code and links for many different FFT implementations and related information.
   http://www.jjj.de/fxt/

Fast Fourier Transforms  
   Contains Fast Fourier Transform source code (C, C++, Pascal), tutorial, and math theory.
   http://www.intersrv.com/~dcross/fft.html

benchFFT  
   Benchmark comparing speeds of many FFT codes. Results from many machines, and code to run it yourself.
   http://www.fftw.org/benchfft

FFT Links  
   Links to many sources of FFT code and information.
   http://www.fftw.org/links.html

FFTW  
   Fast free C FFT library; includes multi-dimensional, real-complex, and parallel transforms.
   http://www.fftw.org/

A Short Demonstration Version of the FFT Source Code in Fortran  
   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.
   http://members.tripod.com/michaelgellis/dsp/pgm05.html

Jens J. Nielsen's Home Page  
   Arbitrary length FFT C-source, 3D gravity simulator, quantization of FIR filter coefficients. C source.
   http://home.get2net.dk/jjn

fftpack  
   A package of Fortran subprograms for the fast Fourier transform of periodic and other symmetric sequences.
   http://www.netlib.org/fftpack/

Row-oriented Multidimensional Fast Transform Library (RMFTL)  
   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.
   http://www.davis-inc.com/rmftl

Sigview - FFT Analysis Software  
   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.
   http://www.sigview.com/

FFT Page  
   Links and various Fortran FFT implementations.
   http://faculty.prairiestate.edu/skifowit/fft/