Phaser is a free and fast 2D game framework for making HTML5 games
Godot game template and component-based framework
2D GPU-accelerated framework for ActionScript developers
a 2D Game Development Framework
A Phaser CE plugin that brings sloped tile collision handling
Super-fast 3D framework for Web Applications
3D .NET engine for Windows, Linux, Mac
Cocos2d for iOS and OS X, built using Objective-C
C++ SDL/Box2d Programming
Box2d Flash Alchemy Port + World Construction Kit