Crystal Space is a free (LGPL) and portable 3D Game Development Kit written in 
C++. It supports: true six degree's of freedom, colored lighting, mipmapping, 
portals, mirrors, alpha transparency, reflective surfaces, 3D sprites (frame 
based or with skeletal animation), procedural textures, radiosity, particle 
systems, halos, volumetric fog, scripting (using Python or other languages), 
8-bit, 16-bit, and 32-bit display support, Direct3D, OpenGL, Glide, and 
software renderer, font support, hierarchical transformations.

WWW: http://crystal.sourceforge.net/