BZFlag is a 3D, multiplayer, tank battle zone, capture the flag game that pits players against each other in a networked environment. It runs on Windows 95/98/NT/2000, Linux, MacOS 10.x, Irix, Solaris, and others. An OpenGL accelerator is highly recommended, but it is playable with 3D in software.
World Foundry is a 3D level game engine and asset production pathway with over 170,000 lines of code. It was originaly created as a commercial product, but is now being released under the GPL. The engine was designed from the beginning to be cross platform, and ran on Windows (DirectX, GL), and the Sony Playstation. The production pathway ran on Windows, and extended 3DStudio Max to be our level editor. The engine is currently being ported to Linux (it runs, but needs work), with plans to port the production pathway as well. Developers are wanted to help with this effort.
BurgerSpace is a game in which you are a chef, and must walk over hamburger ingredients (buns, meat, and lettuce) to make them fall from floor to floor, until they end up on the plates at the bottom of the screen. It requires the SDL multimedia library. It is a clone of the 1982 BurgerTime video game by Bally Midway.
SuperTux is a side-scrolling platform game. The hero in this game is Tux the Penguin, the game's only reference to Linux. On the journey to rescue Penny, who has been kidnapped by evil Nolok, Tux faces 23 different kinds of bad guys while jumping and running through 101 beautifully-drawn levels. The soundtrack is available on last.fm and similar sites.
Cosmosmash is a game where you control a base that must destroy rocks before they hit the ground, or you lose points. You must also prevent "spinners" from touching the ground, or your base will explode. This game is a clone of the 1981 Astrosmash video game for the Intellivision by Mattel Electronics.