lxgui

Note: this project has been migrated to github:
https://github.com/cschreib/lxgui

lxgui is an open source, portable, and data driven GUI. It is fully extensible, and supports caching through render targets. It is meant to be used by real time applications (such as games).
The GUI can be created either by C++ code, or by using the integrated "add-on" system, where the GUI is parsed from XML and Lua files.
It relies on keyboard and mouse input (support for other controllers is not planned).

Front ends are provided for OpenGL (for graphics), and OIS and SFML (for input). An SFML graphics front end is in project.

Documentation : http://lxgui.sourceforge.net/docs