GLFW is a free, Open Source, multi-platform library for opening a window, creating an OpenGL context and managing input. It is easy to integrate into existing applications and does not lay claim to the main loop.
This is the documentation for version 3.0, which has many new features.
If you have used GLFW 2.x in the past, there is a transition guide that explains what has changed and how to update existing code to use the new API.
Last update on Wed Nov 20 2013 for GLFW 3.0.4