If you are looking to spice up your PC case, the guys at Mashie Design have put together a simple set of instructions on how to deck it out in an asteroid motif.
All that is needed is some Styrofoam, Claycrete, and some paint to achieve a convincing texture that looks like it came straight out of space (or straight out of the stone age). [Mashie Design via Unplgged via Gearlog]