Scrupp is a cross-platform 2D engine which uses SDL and OpenGL for visualization. It is controlled by external Lua scripts. The core supports various image, sound, music and font formats. The hard work is done by plugins written in Lua.
Realistically and Acronymically Named Generalized Engine. Sometimes shortened to RANGE or RANGEngine. This is primarily a 2D computer game engine that provides all major functions required. See http://p.sf.net/rangengine/wiki
hiperGL - Is a 2D OpenGL hardware accelerated blitter, graphic loader, frame manager, a DIV like sprite system, and more utilities for creating video games. It works under SDL. It's portable, and easy to use.
NiL is a modular multi-purpose gaming engine including a multiplayer worm game a little like quake, except it's 2d and a little like worms except it's realtime.