Auross
A game engine and game development system.
Auross is a fully object-oriented and multi-threaded game engine. It's designed from the ground up to be portable, scalable, and extensible. The class library is divided into several layers, to allow other applications to easily integrate only the code that's actually needed.
In addition to the engine itself, a comprehensive suite of content-creation tools is also being created. Although actual work on the tools won't start for quite some time, you can help by submitting proposals, comments, and critiques of the tool mock-ups on the OpenUsability page for Auross.
Please Note
I haven't had time to work on Auross in a while, but it's not a dead project. I plan on resuming work as soon as I have some stuff in my life sorted out. I'll make an anouncement when I'm working on it again.