I made a quick demo of browsing Wikipedia categories by popularity. The video is here (sorry about the audio quality): http://www.youtube.com/watch?v=f3QXwY-XR28The source code is here: http://en.wikipedia.org/wiki/User:Wakebrdkid/Popular_category_browsing If other people like having an option to sort categories that way then article traffic might be a good property to store on Wikidata.