Physics Libraries
Physics Abstraction Layer
Open source, free for commercial use. Can select which engine you would like to use from ode, newton, physx, tokamak, true axis, bullet, jiglib, and open tissue. PAL Homepage
Newton Game Dynamics
New Tutorials at Irrlicht Engine Wiki
Old Tutorial at Irrlicht Homepage
Newton Game Dynamics Homepage
Wrappers:
Ode - Open Dynamics Engine
Open Source Physics engine
BSD or LGPL licence
Tutorial at Irrlicht Homepage
Ode Homepage, SourceForge project page
Wrappers:
Tokamak
Tokamak Physics Engine is now released as Open Source Software under the BSD license.
Tutorial at Irrlicht Homepage
Tokamak Homepage
True Axis
Free to use for non commercial.
True Axis Homepage
Tutorial at http://groups.google.com/group/mur_games by Jsmurthy4
Bullet
Free for commercial use, including PlayStation 3, Open Source multiplatform C++ under the ZLib License.
Bullet Homepage
Box2D
Quote from the website:
"Box2D is an open source physics engine written primarily for games. As the name suggests, Box2D is a purely 2D engine. Box2D can now handle convex polygons and other shapes coming soon.
Box2D falls under the permissive zlib License."
Box2D Homepage