I dunno if anyone's done this before, but they do it on a local forum I'm a member of. Basically a different photo is posted every day, it doesnt have to be by the same person, and it doesnt matter if 2 or more people post one, it's just a way that you can show off one of the best photos you've taken recently (it doesnt have to have been taken that day!)
Incidentally, you can post up to 3 photos in 1 post as long as they're within the forum boundaries.
Taken at the Demon's eye gig on Friday night.
canon 400D + 50mm f1.8