A parallel integer only FFT for multi-core micro-controllers like the Parallax Propeller or XMOS devices.
Implementations in various languages are provided.
Muliple cores are used where possible, up to 16, thanks to OpenMP.
Compile the C version like so:
$ gcc -std=c99 -fopenmp -O3 -o fftbench fftbench.c
This may not be the smartest, fastest implementation but it has been used in benchmarking compilers/MCUs like GCC and Catalina C for the Propeller, Propeller Spin and PASM, XC for XMOS and so on.