POV-Ray: a freely available graphics application.

Want to try your hand at some complex 3D modeling or do you just want to make some simple 3D pictures? Either way, the "Persistence of Vision Raytracer" is the tool to get the job done. It is available for Windows '95 / '98, Windows NT / 2K / XP, Windows Vista, Mac OS, MS-DOS, Linux, Solaris, AmigaOS, and more.