Intro to Box2D: physics simulations for HTML5 games
Seth Ladd, a developer advocate at Google put together an excellent, in-depth intro presentation on using Box2D as a physics simulation in HTML5 Game. It covers which port of Box2D to use, getting the world up and running on the page, and performing initial collisions and adding joints. He’s also written a number of in-depth blog posts on the subject which are linked from the appropriate slide.