GLFW

From GPWiki

GLFW (GL framework) is a platform-independant library that does things that would usually require platform-dependant code. Most notably:

Setting up windows and providing an OpenGL context for them
Reading input
Threading
Timing

The library is similar to SDL, except that it does less things that are not strictly tied to the platform, just texture loading. Therefore it is somewhat smaller. Also, the licence for GLFW (Zlib licence) is less strict than the one that SDL uses. At the moment GLFW supports pretty much any Unix with X11, MS Windows and Mac OS X.