HGE

http://animatedream2d.sourceforge.net/

I love HGE for its simplicity and unobtrusiveness. It doesn't make assumptions about the type of game you want to make that end up getting in your way. That said sometimes a more fully featured engine and toolkit that already has most of your work done for you can be nice too.

I have integrated hge, guichan, box2d, tinyxml, tilestudio, and a heck of a lot of my own work, into one game engine. The goal of which is to provide a very thorough and well integrated toolkit for all kinds of 2d games. It is open source. The svn is available from sourceforge for any who want it, and if anyone has suggestions or would like to contribute I would be very grateful.

Please note: This is by no means a finished product. At the moment there is some dirty code that needs cleaning and a few memory leaks mostly involving guichan right now, but I should get around to that soon. That's why the only way to get it is through svn.