I'm the maintainer of JSBox2D, a new JS port of Box2D that is up to date with the Box2D trunk. It is located at https://code.google.com/p/jsbox2d/ - you can find the release downloads, testbed, etc there.
I'm interested in adding support for R.U.B.E. world loading in there, as well as creating a bit more widespread support/exposure for JSBox2D. I was fairly disappointed at the lack of updates for the other myriad of Box2D ports, so I figured I'd go ahead and make one myself.
Since it's more up-to-date than box2dweb, it would be very cool if we'd be able to update your Javascript Demos widget on the site as well. R.U.B.E. is excellent, and we definitely want to help bring the power with the newer versions of Box2D in the JS world

Thanks,
-P