3D File format viewer/explorer
XNA based game engine completely written in c#
shader editor
A cross-platform game framework based on OpenGL and GObject.
Gimpel3D - 2D/3D Stereo Conversion Editor
3D world editor for game development
Pear3DEngine is a modern and modular 3D development framework
Minimalist 3D Scenegraph Management Framework
https://github.com/horde3d/Horde3D