Mark your calendar.
A new comet was discovered last week by Russian Astronomers with the International Scientific Optical Network (ISON). It's currently around 6.6 AU (990 million km) from the Sun which puts it between the orbits of Jupiter (5.2 AU) and Saturn (9.5 AU).
Judging by the comet's size and calculated orbit, a little over a year from now, in November of 2013, this comet may be brighter than the full Moon in our night sky! How awesome would that be!
And no, this isn't a harbinger of doomsday even though some morons on the Internet will certainly start their crazy ass speculations (if they haven't already). The orbit for this comet is already fairly well worked out and it will miss Earth by about 60 million kilometers.
Predicting the brightness of a comet (especially a year in advance) is always tricky business, but this one looks pretty good. Just keep in mind an apropos quote often attributed to astronomer David Levy (co-discoverer of Comet Shoemaker–Levy 9) is "Comets are like cats; they have tails and do whatever they want to do."