The Building Coder blog...
I have not yet published the complete full Revit add-in for this, because I was planning to migrate it from Revit 2013 to 2014 and place it on GitHub first.
However, due to time constraints and popular demand, here is [a download link of] an immediate snapshot of version 2013.0.0.8 of the RoomEditorApp for Revit 2013 in its current state. I already discussed a number of its features. Others have been added since, and I'll go into those in detail when I find time to port this to Revit 2014.
The RoomEditorApp can be found here.
Credit: Luke Johnson's What Revit Wants blog.