The transit of Venus is one of the rarest astronomical events in our solar system. It happens in pairs, every century. This awe-inspiring video shows the first of this century's pair, which happened in 2004. The next one is about to happen—on June 5, 2012.
Update: If you are in NYC, you can also watch it at the Rose Center for Earth and Space, in the hall of the universe, on the astrobulletin—the giant screen downstairs.