I used the Persistence of Vision Raytracer a long time ago with a graphical front-end (at the time it was just command line) and it's come a long way. Check out the 'Hall of Fame' images - this program is incredible for something free! I used it today to create a 3D smiley face to use as the background of the menu. Here's the code to render the smiley.
The Persistence of Vision Raytracer is a high-quality, totally free tool for creating stunning three-dimensional graphics. It is available in official versions for Windows, Mac OS/Mac OS X and i86 Linux. The source code is available for those wanting to do their own ports.