Rubygame is a new library that provides ties between the SDL (Simple DirectMedia Layer) and Ruby, so that you can do graphics and sound work from Ruby, ultimately to build games. It's stylized off of the popular pygame, the equivalent library for Python. Unfortunately it currently only works on Linux (and other Unix-like systems) but Windows and Mac users should be in luck soon.

If playing with OpenGL, 3D graphics, and building some simple games sounds appealing to you, Rubygame is the place to be.