A few months ago we stuck a new game up on Gorillaz.com that I think is great!
It’s built using the the box2d WCK found here http://www.sideroller.com/wck/ that is an awesome system. It’s got a c++ alchemy version of box2d in it so it’s really fast and the world creator kit lets you drag items around in the IDE and even use the timeline to animate bodies.
For this game we created a proxy system that let us layout the levels graphically on stage in their own swfs. This was then replaced with the physics objects from the base swf once they were loaded and added to the stage. After the initial load each level load was just a few KBs, quick to compile and behaviours could be changed for all the levels by editing the base.
All the crazy physics stuff was topped off with some really great graphics from Adam Gale. The last level of the story mode where you’re floating round inside a whale is brilliant!