Hi,
I have been working for quite some time on a REST interface for ROS systems (based on python) : https://github.com/asmodehn/rostful.
Very useful for introspection into running multiprocess systems and debugging. Better client code for visualisation would sure be a big help, but I am currently focusing on a more critical part : getting the web server interfacing with ROS right…
Since a big part lacking in ROS is documentation/support/tutorials for developing reactive systems, I have been thinking of investigating using http://elm-lang.org/ in a web cient to offer a graphical view of a running ROS systems. I didnt get around doing it yet… If it s something that interests you, it can be quite self contained I think… And I think it would be an interesting experience for the people interested in web system development for ROS. There also, the tricky part will probably be interfacing with ROS.
You could remake the usual ROS turtle simulation tutorial, but web based, just for fun 
Or remake some QT tools, or of course just pick you own idea… Feel free to ping me if you want more info about any of these.