It uses colour-table animation to fade between a bunch of words in a mildly distracting manner. It's free, but please send me some email if you like it.
Be warned: ShapeFader will try to change your monitor to 8-bit colour (and if it fails, it will simply stare blackly at you). It hasn't been tested with many macs yet; if it crashes, let me know as much as possible about your Mac and system. (I'm not sure yet if it will run on macs running in 24-bit mode which have their monitors in 32-bit memory.)
Suggestions for a better name are invited. So are suggestions for interesting words to add to it. (Preference is given to words with more ambiguity in this context -- for instance, words which can be read as adjectives or nouns.)