for those of you worrying (needlessly) about the many end-of-the-world scenarios that have been put forth to occur (in)conveniently on the exact same day - december 21st, 2012 - there is a nice description by cameron hummels in today's podcast of 365 days of astronomy!
Summary: An increasing number of people believe that December 21, 2012 will mark the end of the world. Proponents of this idea cite diverse astronomical reasons for an imminent apocalypse: the end of the Mayan long-count calendar; an alignment between the Solar System and the Milky Way; the solar sunspot cycle reaching an all-time high; the reversal of the Earth's magnetic field; and a devastating collision with 'Planet X'. Tune in to hear to the facts and controversy surrounding this purported impending disaster.
i will inevitably write more about this topic as the date approaches because people have asked me a lot of questions about these issues and i'd like to clarify what are facts and what are fallacies. to summarize: no, i am not worried. i have not heard a single doomsday claim that is supported by facts.
for more information, read what ian has to say at universe today.