here's a class for supercollider that generates perlin noise. i wrote it about a year ago to learn how that works but didn't finish the helpfile until now.
some examples of images made with this class...
and this is an example from the helpfile that gives an overview of some settings of 'persistance vs octaves'. the 8 steps of persistance grows from 0.25 to 0.95 left to right. and octaves grows from 2 to 9 bottom to top.
(update 090523: RedPerlin is now part of the redUniverse quark)