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.

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 proprietary 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.