At Three Ways School we recently purchased an Optoma ML750ST projector for dedicated floor projection. This is an awesome little projector, it is tiny, has a short throw lens and an LED light source. I'm using it with an overhead IR camera to do some interactive floor projection which I programmed in Max MSP. Check the video:

Interactive floor projection built for Three Ways School (Bath) Sensory Studio. Built using Max MSP. Really should have disabled the auto focus in this low light...