Zoo : Multi-System Emulator
Zoo is the longest-running software project I've ever worked on, including my actual work as a professional software developer.
Developed by uchinokitsune@ and myself, we originally began by designing a Sega Dreamcast Emulator called "Penguin", but it slowly morphed into writing our own JIT compiler ("fox"), writing multiple processor cores, graphics and processor debugging tools.. It has grown to include a very basic PS1 emulator (It can run through a few games completely), as well as an emulator for our "fantasy console", Dragon.