Below is a snapshot of the screen saver running in the Quartz Composer viewer. It is a rotating cube with each face showing an uncalibrated intensity map from a raster taken sometime in 2007 if memory serves me correctly.
Click on the link to download the screensaver and place the .qtz file in /Library/Screen Savers/. On my Snow Leopard (10.6.8) machine these screen savers appear in the "Other" section in the "System Preferences / Desktop & Screen Saver" options. Things may be different on a Lion machine. Oh yes, Mac OS X machines only I'm afraid.
As it's a .qtz file you can double-click it to launch it in Quartz Composer, look at the source and edit it of course. This particular composition is ridiculously easy to do.

Download Screen Saver

Quartz Composer images used to run in web browsers but now all you get is this...

... which is a shame.

I plan to make more screen savers when I have time because Quartz Composer is fun to play with. Quartz Composer has improved so that now each face of the cube can hold a different image, which could be fun...