Selador is a browser-based fantasy game. The game was commercial at first, but has since been released as open source by its developers. The game focuses on teamplay and communication between players. Although it is played in real-time, strategy and planning are paramount. It comes with a nice set of graphics and a pre-populated database. It can be installed on any *AMP stack.
Whiteshoe is a text-based shooter game in which you explore a changing maze and complete your goals before the other players complete theirs or find you. It is based on the old game hunt, but was totally rewritten from scratch to use TCP packets and be more modular and expandable in design.