A few people have been throwing around the idea of a PHP / JavaScript demo, and the first thing that popped into my head was the use of AJAX.
It is possible to hook the AJAX output into a canvas at the client side, and a database on the server side.
Users should then be able to post messages to the database (like a shout box) which are read back in real time into the canvas, which applies effects to the text, such as rendering it as cubes or some other inventive method.
I'll see how far I can run with this idea.