OpenGL.org is the official site for OpenGL news and information.
Mesa is a free 3D API very similar to OpenGL. Useful for developing on Linux.
GLUT is the simple cross-platform windowing toolkit on which GLOW is built.
GLUI is a widget library built on top of GLUT, similar to GLOW.
GLOW is licensed under the GNU LGPL.
Here is a large list of graphical user interface frameworks and toolkits.
The home page of the author, Daniel Azuma
Daniel Azuma (email@example.com)