Dynamica is a Maya plugin based on the open source Bullet Physics framework. Originally developed at Disney Animation Studios, the toolset has been enhanced with additional features and art direction friendly workflows. I worked on the project as a developer in from Fall 2010 - Summer 2012 and presented the new features at the Siggraph 2011 session titled Destruction and Dynamics for Film and Game Production. More Info:
Project page on Google Code: http://code.google.com/p/dynamica/
Siggraph 2011 session notes: http://bulletphysics.org/siggraph2011/
Wiki documentation: http://bulletphysics.org/mediawiki-1.5.8/index.php/Maya_Dynamica_Plugin
Bullet Physics page: http://bulletphysics.org/