This forum was created by a good friend of mine, Erwin Coumans, and someone with whom I worked at Havok and with the company that developed Blender ( the open-source 3d modeler / game engine app ).
http://www.continuousphysics.com/Bullet/phpBB2/index.php
Many of the leading physics programmers discuss various physics based features on the forum.
You can also download and use Erwins own physics engine ( Bullet ), in both open-source and commercial projects.
Regards…
Mal