Apologies if it's been posted before, but blast it I want to say it:
The Mayan calender does NOT end in 2012, it LOOPS BACK. During a Mayan Calender Round that occurs once every 52 years the Mayans believed they went through a period of bad luck and misfortune. Most Mayans considered living to see the calender reset during one's lifetime was an incredible honor. (Recall the average lifespan would have been somewhere between 35 and 45 years.)
Most people think that because the Olympic Games, U.S. Presidential Election and various other events taking place in that year, it'll be big. Most Mesoamerican scholars scoff pretty heavily at the whole thing.
The next Mayan calender round occurs December 21st, 2012. The Mayan calender doesn't number it's days, technically, only years.
What will I be doing? Hopefully Starcraft 2 and Diablo 3 will be out by then, cause dang I needs me some awesome!