The 2011 Washington Post Peeps Diorama Contest. I'm not as enamored with the entries this year, as I think you need more than just sticking two or three Peeps in a movie/TV show/other pop culture reference, and there seem to be a fair amount of those. Also, too many bunnies, not enough chicks.
That having been said, I do like the Muppet Show (clever Peep alteration), the arcade "spot the difference" scenes, the Metro station (the computerized sign is great, though system familiarity helps), the Angry Peeps, and Noah's Ark.