Blobber's become a pretty cool piece of software in a fairly short period of time. You can select different colours to draw with, and can even track multiple lasers so more than one person can draw at the same time.
We had a good time using lasers to draw all over the base of the statue of John Calhoun, creating no mess and leaving nothing behind after we finished.
If you're interested in finding out more about it, we'll have it set up at our upcoming Linux Demo Day on September 14 at Muddy Waters in West Ashley (1331 Ashley River Road) from 1-4PM. Come on out and join us!