UCI chess engine
Odamex is a free, cross-platform, modern client-server Doom engine
VR Mosaic - C++ Builder Applet v.2.5
Real-time RPG for PC/tablet/phone; multiple quests and random dungeons
scriptable game engine with built-in support for 2D graphics and sound
Extremely hard-core lander game.
Game development toolkit
Explore with geometric curves. Create images of spirograph curves,
A cross-platform OpenGL based lightweight scenegraph library
Qt4-based dogfight simulator inspired by Sopwith
Vector based drawing software designed for RPGs