Urban legends are stories that are either funny and/or contain horrifying content that may or may not be true. They spread quickly, and often have many different variants. Most urban legends are false -- but some are true... Here's a couple of nice examples:
Osama bin Captured? : Osama bin Laden was captured long ago, but the U.S. government is keeping this news under wraps until just before the 2004 Presidential election.
Playing Ketchup: HIV+ blood has been slipped into ketchup dispensers in fast food restaurants.
CPUSA: The Communist Party USA is endorsing John Kerry for President.