SIMFONIA (http://www.simfonia.fr/SAT/) (free or Pro)
A plugin animation for Windows / Sketchup (free or Pro)
The free version works with 10 objects and 10 seconds!
Sufficient for some crazzy animations!
Complete documentation on line as PDF (English/ French)

Video (http://www.youtube.com/watch?v=8mu5gJY6rP8)