OpenArena is a 3d game creation engine. It is a rendering system that can be used for more than just games but it is targeted at games. The basic use being create some game media textures models maps and config files for physics and rules.
RubikSim is a 3D Rubik Cube Simulation, featuring mouse controlled cube rotation and manipulation using a virtual trackball model. RubikSim is written in C++ presently using MFC and OpenGL. A wxWindows port is planned.