XML Simple Parser is a parser and generator for xml files which is kept as easy and lightweight as possible. Its intended for use in games or other applications to store data in xml files and for sure also for reading it from there.
The Simple Object-Oriented Game Library is basically a simplification of SDL with some nifty features. SOOGL is used in a C++ course at Mälardalen University (http://www.mdh.se) and is mainly intended for beginners.
SAGE stands for Simple Asynchronous Game Engine and is an attempt to implement a multithreaded game engine in C#. For rendering/physics/sound/etc it uses(/will use) open source libraries (like OGRE, ODE, etc) through plugins.