NERO
- Game and engine that revolve around "training" AI robots to engage on a futuristic field of battle.
- http://z.cs.utexas.edu/users/nn/nero/

comisat Games Collection
- GPL licensed multiple game package featuring classic game remakes including Connect4 and Tetris.
- http://comisat-games.sourceforge.net

WINE
- Not directly a game, but a set of APIs that can be used to port Windows games to Linux or to run them directly.
- http://winehq.com

D2X-XL
- Aims to create a better Descent 2 in OpenGL. Maps, levels, and sourcecode are available.
- http://www.descent2.de/d2x.html

Lost Labyrinth
- Modern graphical rogue-like game. Currently in a release state, it is also under constant revision. Source available.
- http://www.lostlabyrinth.com/

XArchon
- Play-alike of Archon which was created by FreeFall Associates and distributed by EA.
- http://xarchon.seul.org

GTK Cervi
- Clone of the game called Cervi (Worm). It is a multiplayer game (on one machine) where players drive worms and mustn`t collide with anything.
- http://nomi.cz/en/projects.shtml?id=cervi

Cedega
- Commercial re-implementation of the Windows API for Linux with a focus on gaming. Similar to (and a derivative of) WINE.
- http://www.transgaming.com

OpenCity
- Free 3d city simulator written from scratch using OpenGL and SDL.
- http://opencity.sourceforge.net

Battle for Wesnoth
- Polished turn based strategy game featuring fantasy characters and modular plots.
- http://www.wesnoth.org/

WorldForge Project
- Aims to produce an immersive environment engine for high quality games. It is both a community and a game engine with game implementations already finished.
- http://www.worldforge.org/

Vega Strike
- Elite like space sim and game engine with modern rendering and capabilities.
- http://vegastrike.sourceforge.net/

XFrisk
- Networked X11R6 (Unix GUI) "Risk" like boardgame
- http://www.tuxick.net/xfrisk/

Gamma Patrol
- Old-style vertical scrolling space-shooter. Fight your way through enemies using different weapons.
- http://www.odahoda.de/avop/gammapatrol

Gem Drop X
- Fast-paced puzzle game where it's your job to clear the screen of gems before they squash you.
- http://www.newbreedsoftware.com/gemdropx/

gtkmonop
- GTK+ client to monopd. Monopd is a daemon for playing monopoly over the Internet.
- http://gtkmonop.sourceforge.net

Powermanga Linux
- Arcade 2D shoot-em-up game with 41 levels and more than 200 sprites.
- http://linux.tlk.fr/

Defendguin
- New Breed Software's clone of the Williams arcade classic "Defender." Instead of humanoids, you rescue penguinoids.
- http://www.newbreedsoftware.com/defendguin/