Sphere is a RPGCE (a role-playing game (RPG) creation engine) that allows you to relatively easily put together an RPG along the lines of Final Fantasy 6 or Phantasy Star. It supports 32-bit graphics (with 256 levels of translucency) and MP3, Ogg, MOD, S3M, IT, and XM files for audio (and WAV and SPX (speex) for sound effects), and does not place arbitrary limits on map, tile set, sprite set, or script sizes.
Phaos is a browser-based MMORPG. It features character creation, the ability to purchase/sell/drop potions, weapons and armor, traveling, inter-player chat, the ability to fight in the arena, explorable dungeons, an admin system, the ability to trade with other players, and the ability to fight other players. A download is available for people running Windows who do not have access to or do not want to set up a Web server.
"The Game" is a project designed to simplify the process of producing any high-quality cross-platform 2D or 3D graphical computer game. The hope is that any game can be produced simply by changing a few settings and pressing a "compile" button. The project has three "deliverables": a game engine library to abstract across the set of all possible computer games (applying object-oriented design methods to the general problem in such a way as to be usable in specific instances); a graphical interface for easy game design (an exercise in human interface design); and a gaming package with a lot of shiny games to play.
webDiplomacy (previously phpDiplomacy) is a Web implementation of a popular turn based strategy game in which you battle to control Europe. It is not a game of luck: to win you must be diplomatic and strategic, forming and breaking allegiances and bargains with your friends and enemies. It features an interface intuitive and simple enough that seasoned Diplomacy pros and complete newcomers can play alongside each other.