Pooh_Bear has slowed down some other songs, but I might point your attention to his sped up version of Otis Redding's "(Sittin' On) The Dock of the Bay." There's a hint of some Amy Winehouse in there, too. Who know either speeding up or slowing down songs by Otis Redding and Amy Winehouse would make either artist sound a lot like each other?
Someone also slowed down Justin's Bieber's "U Smile" by 800% this past August, and has its own weird, Sigur Rós effect to it.
None of these, unfortunately, hold a candle to the slowed down version of the Olsen Twins' "Gimme Pizza." It's impossible to be that creepy/vividly entertaining at the same time.