3D game engine/framework in C, with Luajit and Python bindings now
GemRB is a portable open-source implementation of the Infinity Engine
Cooperative multiplayer graphical RPG and adventure game
For exploring cellular automata like Conway's Game of Life.
4X Space Strategy Game
Arianne is an engine to develop multiplayer online games like Stendhal
OpenSource and DIY real electronic darts game
A game engine for console based text games
Framework for producing web-based database applications
A Sudoku puzzle game
Open source revival of the game Transarctica / Arctic Baron
Defeat all the beasties to claim victory!
Snakes of Apocalypse is a funny multiplayer game
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Carcassonne clone written in python using pygame
A roguelike, contains binaries and source packages for
Character animation system for games and simulations.