A Wargame
Play the role of a virus in a quest to replicate.
Javascript adventure game engine
Yet Another Chess ENgine
Combat simulator for the browser game Light Of Nova.
A game engine in java for 2D strategy games
Anathema has moved to http://anathema.github.com
EPIC is an indepth Multiplayer Strategy RPG Web Game
The classic intelligent role playing game
A tool for roleplaying gamemasters
It allows you to teach/learn concepts visually
Spykee Control Interface in Java
Just aims to be a chess board (free to make your moves).
An extension to Buildcraft's Power System. Also includes new machines.
A ball-and-paddle style game
A free Python 3 text-based MUD game server
Free and open source FPS based on Quake III Arena
WarNards is an advanced version of backgammon.