David Ehlers

2D ActionScript 3.0 Physics Engine

APE (Actionscript Physics Engine) is a free AS3 open source 2D physics engine for use in Flash and Flex, released under the MIT License. APE by Alec Cove. 

This thing is more fun than Gears of War. Heck, it even has Mochi as an element

http://www.octaveengine.com/en/

” OE-CAKE! is demonstration software for 2D-based multi-physics simulation. 
In a way similar to drawing images using paint software, users create objects and can see them move according to the laws of physics. This software supports various physical materials with real life properties such as fluids, gases, rigid (hard) objects and elasticity (soft) objects as building blocks. Users can combine these objects to create and play with more complex objects and mechanisms such as cars, gears and moving dolls. Users can also attach pictures and photos to objects and change their shape, break them apart, or melt them. ”

Physics engine for flash in 2D - Box2DFlashAS3 is an open source port of Erin Catto’s powerful c++ physics library.