I've been porting StuntPlaygound to MacOSX. It uses the Ogre3D engine. The source was kindly provided at http://walaber.com/. The main challenges have been getting to run on the latest version of Ogre ("Eihort", 1.4.x), which uses CEGUI v0.5 for UI elements and OIS for keyboard and mouse input.
So far, I have the arena spinning around and the logo comes up: