PCSX2 is a PlayStation 2 emulator for Windows and Linux, started by the same team that brought you PCSX (a Sony PlayStation 1 emulator), with continuing contributions from open source developers.
PCSX2 is one of very few fully functioning PS2 emulators available today, with both high compatibility and high performance. Many games still emulate slowly due to the inherent complexity of the PS2's architecture, but on whole the emulator is functional and enjoyable.
PCSX2 has changed repositories a few times over the past year. Code metrics for contributions made from 2005 to 2008 can be found at the following Ohloh pages: