Space.com's running this nice summary of the space junk problem facing us today. At least some of those things might be Saturn V and 1-B boosters, which, considering their size and essentially hollow nature, might make decent space stations one day. Otherwise yet another opportunity for "New Jersey Waste Management Officials". ;)
Update: BBC news is running this piece which offers a much better explanation of how a Saturn V 3rd stage booster could end up orbiting the earth. This is what they built Skylab out of, so if someone had the technology to catch it, it would make a pretty nifty space station.