I just leave them in there and camp out to make sure I get first dibs on the next free washer/dryer. I live in a huge apartment complex and there's usually several machines free, but I got stuck doing laundry one crappy Sunday afternoon and spent over an hour in the laundry room with a book waiting for a free dryer.
I'd feel like a scumbag if someone caught me emptying their clothes out of the dryer, although the people who don't come and get their clothes within a few minutes piss me off. If I have a choice, I'll do laundry first thing on Saturday mornings when the manager unlocks the laundry room at 8:00, so I can beat the rush....