My world is of a roller coaster (written in C++ / GLUT / OpenGL). To build the track, I used B-Splines to interpolate between fixed points. I added five spheres to move along the track. I also used the the normal, binormal, tangent vectors at each interpolated point to determine the rotation of the spheres. My world also has a directional light representing the sun.
Warning: May only build (as is) on OS X. Hasn't been tested on the Unix machines.