Gavin Wignall has posted an example which was done inside Blend using behaviours added from the Farseer Physics Engine.
This example took minutes to throw together, in fact I spent more time watching the cool crazy mayhem that it created than building it!
I have not had enough time to fully thrash out this add-ons potential, but first impressions lead to some very ‘easy to use’ cool features that will greatly expand your ‘bag of tricks’ in the Silverlight world.