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.
Cadaver is a simulated world of cyborgs and nature in realtime. The battlefield consists of forests, grain, water, grass, carcass (of course) and lots of other things. The game server manages the game and the rules. You start a server and connect some clients. The clients communicate with the server using a very primitive protocol. They can order cyborgs to harvest grain, attack enemies or cut forest. The game is not intended to be played by humans! Instead the idea is that you write artificial intelligence clients to beat the other artificial intelligences.
XPilot is a graphical multi-player maneuvering game with less-exciting graphics, but more speed, tactics, and insults. Some people also use it for UDP network analysis. Over the past eight years of playing and development, tons of features have been added to the game, from basic weapons like shotguns and missiles to more recent ones like phasing devices, invisibility, or hyperjump.
EC-Laby is a small net-game with 2 teams of players running through a labyrinth to find the startroom of the other team. The first team which reaches the other startroom wins. There are features like chatting with other players and collecting points, and abilities to view a lab-map, set orientation points, insert oneways in the labyrinth, beam to other players, and insert question-doors in the labyrinth.
Babelize is a collection of localizations for Linux games. It currently features French, German, Polish, and Spanish translations for "Heroes of Might and Magic III", as well as French, German, and Spanish translations for "Alpha Centauri - Alien Crossfire". The goal of the project is to provide localizations for as many native Linux games as possible.
Widelands is an economic and military simulation game. The map is shown in parallel perspective with 3-dimensional terrain. Buildings and units are animated. The player controls a tribe. Land is claimed and held by military presence and then used to build an economy to support military expansion and confrontation. The project is a work in progress where much remains to be done; computer players and multiplayer are in very early stages of development. Some features that have already been implemented are exploration, fog of war, sound effects, background music, adjustable simulation speed, a few tutorial campaigns, translations to several languages, and a map editor.
GalaxyHack allows you to design a fleet of spaceships which can then be tested in AI script based battles against fleets designed by other players. Though battles take place in real time, the strategy comes beforehand, both in writing short AI scripts in an easy-to-use proprietary scripting language, and also in the set up and selection of your forces.