It will indeed be the end of the world (as we know it) .. which is a shame because that day is also someone's birthday.
4 Ahau 3 Kankin... Affectionately known as "snake day", the 21st of december in 2012 marks the end of the Mayan calendar. The planets will align with the center of the glaxy, our microwaves will act stupid and burn our popcorn, and people will go crazy on the streets. Nothing else will happen. However, the superfluous spending people often do prior to Christmas will be virtually non-existant since so many people truly believe there will NOT be a Christmas, the economy will tank to all time lows and the rift between the rich and poor will almost instantaneously be too overwhelming to bridge. The global economy will suffer greatly and many more people than usual will die in poverty.
That is provided the poles don't switch. If they do, Santa will get lost in an effort to get back home and will wreak havoc upon the earth, destroying us all.