PyPy is both an implementation of the Python programming language, and an extensive compiler framework for dynamic language implementations.
A simple CPUID decoder/dumper for x86/x86_64
A C++ library with various uses.
SheepShaver, a PowerPC emulator capable of running Mac OS 7.5.2 through 9.0.4
A game engine by Uplink Laboratories and Ferrous Moon
A git-compatible SOCKS-based proxy tool.