The Graffiti Research Lab (the folks behind the LED Throwies) have just launched another project called Interactive Architecture. Basically it involves leeching some power from streetlamps and using a projector to beam interactive works onto the side of buildings. I like the generative stuff that uses the windows of the building as nodes, very smart. Of course you can download the source code too if you want.
Apparently this technique is called “Projection Bombing” and you can find out all about it at the Instructables website.
Here’s the YouTube version of the clip below, but be warned, the music is crap.
(Thanks to Danielle at Binalogue for the link).