TX Library is a tiny graphics library for Win32 written in C++.
Orx: Portable Game Engine
Open Game Bootstrap
Cross platform Game Creation Software
A generic 2D engine for any kind of game
A basic 3D environment with a first-person POV
TurboSphere is an easy to learn and powerful JS based game engine.
Scriptable frontend for media applications.
A very small multi-platform game engine for creating desktop games.
Cross-platform reimplementation of AMOS BASIC (runtime)