Matter.js is a 2D rigid body physics engine for the web. It supports compound bodies, concave and convex hulls, physical properties, restitution, collisions, stable stacking, friction and resistance, constraints, sleeping bodies, etc.
Code Libraries: Physics
A lightweight physics engine, written in CoffeeScript. It works with the canvas, the DOM and WebGL.
box2dweb is a physics engine ported from Box2dFlash which, itself, was a port of the original Box2D.