A simulation created in Starry Night of an asteroid (650) Amalasuntha transiting in front of the planet Jupiter as seen from the southern hemisphere of Earth on December 22nd, 2011. The event will probably be non-observeable, as the asteroid is less than 13th magnitude. While it looks close, Amalasuntha has an orbital distance of about 2.5AU's from the Sun, while Jupiter is about 5.2A.U.
Ed ~ The transit occurs at ~17:20 UT to 18:32 UT, and and be observable from southern Africa and the Indian ocean