There is one thing that keeps coming back to me, which is 3D projecting. How cool would that be? But how how does it work? Is it even possible?
I found this video online, which tells how 3D projecting is done: http://vimeo.com/7047856. This technology is designed to project on a stage, using a special foil to create the illusion of a free-flowing image. This means you cannot walk freely around the projection (when you see Madonna walk around the Gorillaz in the video, she is also a projection).
The image is projected from underneath onto the foil, which is stretched across the stage in a 45 degree angle. The foil is nearly invisible where it is not hit with light, so it appears that the projected images are free-flowing in the stage. I would like to see this for real, as I think you might notice the foil or see that is not actual 3D.
Can you also project light in a cloud of fog? Or would you still see the rays from the projector? If this would be possible, you could paint with light and the trail of light would be visible live, as you are drawing. That would be really amazing.