There's a lot of hype right now about the Mayan calendar, but it's interesting to note that none of it is coming from experts in Mesoamerican studies. In fact, it all seems to be coming from people trying to sell something, from books to movie tickets to emergency supplies. A couple of sites out there might help you rest assured there's nothing to be worried about.
An article in USA Today explains that "Part of the 2012 mystique stems from the stars. On the winter solstice in 2012, the sun will be aligned with the center of the Milky Way for the first time in about 26,000 years. This means that 'whatever energy typically streams to Earth from the center of the Milky Way will indeed be disrupted on 12/21/12 at 11:11 p.m. Universal Time,' journalist Lawrence Joseph writes. But scholars doubt the ancient Maya extrapolated great meaning from anticipating the alignment — if they were even aware of what the configuration would be. Astronomers generally agree that 'it would be impossible the Maya themselves would have known that,' says Susan Milbrath, a Maya archaeoastronomer and a curator at the Florida Museum of Natural History. What's more, she says, 'we have no record or knowledge that they would think the world would come to an end at that point.'"
The news site of the Discovery Channel has an article titled "Top Ten Reasons Why the World Won't End in 2012" with a nice summary of arguments against the most frequently proposed doomsday scenarios.
NASA has a FAQ about 2012, in which they explain, "Just as the calendar you have on your kitchen wall does not cease to exist after December 31, the Mayan calendar does not cease to exist on December 21, 2012. This date is the end of the Mayan long-count period but then -- just as your calendar begins again on January 1 -- another long-count period begins for the Mayan calendar."
I'm fond of The Skeptic's Dictionary, and they've come through with a nice entry that explains the complexities of the Mayan calendar in some detail (and which many doomsayers seem to be ignorant of). They also fail to find any reason to think that the Mayans were making a prediction at all, and ask the question, "what is the likelihood that a civilization that couldn't use its vast knowledge to save itself from self-destruction was concerned with predicting what would happen in a future millennium? The Mayan leaders couldn't see far enough into the future to plan for and solve the human problems they faced: too many people on too little land, destruction of their own environment, farming techniques and deforestation that depleted soil nutrients, droughts (partly brought on by their deforestation programs), and so on."
You have to give Hollywood credit -- they've timed the release of the big-budget disaster film 2012 just about perfectly. If nothing else, it certainly looks like an impressive bunch of special effects. I love how Roger Ebert calls it "the mother of all disaster movies (and the father, and the extended family)."