Jeff Paries, Silverlight MVP and author, presented two weeks ago at the Portland Silverlight User Group on using the Farseer Physics Engine in Silverlight. This was an amazing presentation. I was blown away by what could be accomplished just by wiring up behaviors in Expression Blend. It's as simple as drag and drop, really.
NOTE: We're now recording each PDXSLUG meeting, so if you ever miss one you can check it out http://vimeo.com/pdxslug.