CVS repository: https://russ.yanofsky.org/viewvc.py/lost
Written as a project for an AI class. It plays a card game called "Lost Cities" with 3 other players. I did very little testing on it, so I'm not sure how good it actually is, but I do like the design and strategies used.
The source is very well documented. It was written in Metrowerks Codewarrior for Windows. It also compiles with GCC and runs on Linux and Solaris (makefiles included).