Major news outlets are currently reporting that Osama bin Laden was killed by a US missile/bomb some time last week, and for the past week we've been verifying that it was him. Obama is set to address the nation soon. You can watch it live here and at other locations.
Contrary to earlier reports, Osama was killed during an assault on a compound just outside of the capital of Pakistan earlier today, not a bomb last week. He was apparently shot in the head, though it's not clear if we simply executed him or if he was resisting capture.
More info here.