maybe you will love this explode function of the Free SketchyPhysic2 of the Free Google Sketchup ;)
http://www.divshare.com/download/3580244-610
(unzip and launch the file explode.htm with your favorite navigator)
Of course it's not an automatic function, you must attach a movement to each pieces, but it's easy ;)
http://code.google.com/p/sketchyphysics2/