I’ve been playing around with the canvas element recently as I’m interested in the possibility of using some advanced HTML5 stuff in my current pet project
Having also had some previous experience with physics engines and knowing how awesome the results can look, I started to search around for a webby equivalent of either Box2D or Bullet.
I eventually came across Box2DWeb. While not super up to date, or even particularly optimised, it seems to do the job pretty well. Having tried it out on the iPad, the speed is none to shabby.
If you are using a modern web browser you should be able to see the results for yourself! Hit the refresh button to start the simulation again.