Trying to decide on a library for creating a window and capturing user input for my OpenGL app, but there are just way too many choices:
SDL allows you to create an OpenGL context that is accelerated (depending on drivers / hardware support).
I know you tagged as C++, however pygame (python) is a great library for creating 2D games, which also supports an OpenGL context. Pygame is built on SDL.
Clutter is a new OpenGL based GUI library with bindings for Perl, Python, C#, C++, Vala and Ruby. I haven't used it myself. From the website:
Clutter uses OpenGL (and optionally OpenGL ES for use on Mobile and embedded platforms) for rendering but with an API which hides the underlying GL complexity from the developer. The Clutter API is intended to be easy to use, efficient and flexible.