(Try 720p resolution) Here is a screenlapse showing the creation of a complex scene with my Box2D editor, which I am considering calling the Really Useful Box2D Editor, so I thought a R.u.b.e. Goldberg machine might be appropriate for it's first public outing.
As you can see the editor fits into the standard C++ testbed. You can switch into the editor to modify bodies, fixtures, vertices and joints, and then switch back to the normal run mode and continue. Data is saved as JSON using the b2djson utility.
This scene took about 2.5 hours to construct.
See for Box2D JSON loader information, source code and demos.
For details on the RUBE editor see