The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
2D game development library for Ruby and C++
Cross-platform 2D game engine (+ full OpenGL, +full OpenGL ES )
Blueshift is a cross-platform 3D game engine implemented in C++
Multi-threaded game engine for Android
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3