ClanLib SDK was recently released.
(ClanLib is toolkit library with a BSD style license)
OpenGL specific changes from the previous release (2.1) include
- Added support for geometry shaders
- Updated API to reflect the OpenGL 3.3 specification
- Implement the OpenGL PixelBuffer Object
See the examples at: http://clanlib.org/wiki/Examples
Feel free to use any of the source code in your applications.