Hanno Böck has an article on LWN.net on the fuzzing tool afl, American Fuzzy Lop, created by Michał Zalewski of the Google security team:
AFL is a powerful fuzzer, and the above article is a good introduction. There are some more extensive tutorials on afl site, as well as the Fuzzing Project site. Hanno created the Fuzzing Project, which uses FOSS fuzzers to find and fix defects in core FOSS projects. Besides afl, there’s a Python attempt at a version, for those that prefer Python.
(I wish there was more widespread usage of AFL in coreboot, tianocore, U-Boot, SeaBIOS, especially now that SMM is inside OVMF now…)