Polygonal Labs is building a Motor Physics Engine (unreleased) and here is a test that has boxes stacked up that you shake. I am looking forward to the Motor Physics Engine by Michael of Polygonal Labs after going through APE Physics engine by Alec Cove which is pretty slick.
The tools so far by polygonal labs such as the AS3 Data Structures for Game Developers have been excellent and made it into many games and engine tests of mine and his blog is a really well presented and the topics are always well presented and researched.
Also if you don’t regularly visit polygonal labs you are missing out on some really good research and tools. The recent post with the graph-based A* sample using the AS3 Data Structures for Game Developers was killer.