Odamex is a free, cross-platform, modern client-server Doom engine
A cross-platform port of Hexen II game.
3D racing game with Sci-Fi elements and Track Editor
GemRB is a portable open-source implementation of the Infinity Engine
0 A.D. is a free, open-source, cross-platform real-time strategy game.
GLScene Engine for Delphi & C++Builder VCL Windows 32/64
WW2 U-boat simulation
Hardcore 3D space shooter with spaceship upgrade possibilities.
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.
Air traffic control tower and radar simulator (solo + multi-player)
Zoomable user interface (ZUI) with file manager, file viewers and more
A free 3D game engine to create games and realtimes scenes for Windows
LDraw™ editor for LEGO® style digital building instructions.
Game library for Pascal
A real-time 3D Engine written in Ada
Game engine supporting many 3D/2D formats and graphic effects
X3D is the open-standard format for 3D graphics scenes on the Web.
An isometric arcade-style game of skill, puzzles and exploration