I was continually amazed by the wasteful nature of my former neighbors at my old apartment building. I scored a good amount of stuff following moves, including:
A set of wooden swivel barstools, in great shape
A rolling Stanley tool center, in perfect condition with assorted screws and nails in one of the drawers and half a roll of duct tape
An unused queen sized comforter in its original packaging, still in a big JC Penny's plastic bag with the receipt
A Rubbermaid five-drawer rolling container
A Casio keyboard, in its box with the manual and electrical cord
A set of two Coleman folding canvas bag chairs
I would also see half-full containers of cleaning supplies, and on more than one occasion I'd find shitty old lamps tossed with the working CFL bulbs still in them - I scored at least five of them during those years and I'm still using all of them at my current place.
The best find, however, had to come as a result of some unfortunate dude getting kicked out by his better half. I was tossing my recyclables earlier this year, during the first round of the NHL playoffs actually, and I saw a box of pint glasses (shitty, mostly cracked or broken) that also contained a Blackhawks hockey puck signed by Tony Esposito.