John the Ripper jumbo - advanced offline password cracker, which supports hundreds of hash and cipher types, and runs on many operating systems, CPUs, GPUs, and even some FPGAs

tiny HTTP parser written in C (used in HTTP::Parser::XS et al.)

HWRaid: Free code from http://hwraid.le-vert.net

file live sync daemon based on inotify/kqueue/bsm (Linux, FreeBSD), written in GNU C

Allotment Routing Table