Squarely in the “because you can” category: YouDisco is a research project at New York’s Eyebeam that simultaneously streams up to eight YouTube videos onto a rotating virtual disco ball. Frame rate is … well, impressive given what it’s doing. The project is the work of Jennifer Jacobs at Eyebeam “with the help of Jeff Crouse.”
http://youdisco.jenniferj.net/?id=51
What is interesting about this is that you do get interesting effects on a computer screen when you leave 4:3 rectangles behind, just as in projection.
Along the same lines, though focused on a mash-up of two videos side by side (sometimes to hilarious effect):
http://www.youtubedoubler.com/ (which is, for me, playing Shatner yelling “Kahn!”)
Lots of interesting graffiti and motion and illustration work on Jennifer’s blog, like this piece:
Nurse from jennifer jacobs on Vimeo.