The Daily Grail has a great summary of the relevance of 2012 and why you should care. Link.
• December 21 - End of the great cycle of the Maya calendar's Long Count and a 26,000 year planetary cycle in the Aztec calendar, and thus the alleged end of our world (the end of the cycle is dated December 22 or December 23 by some calculations).
• According to the 1997 book The Bible Code the world will end due to a collision with a meteor, asteroid or comet.
• Interpreted by Millennialism as a time when there will be an evolutionary change in human consciousness brought about by a series of world changing events or revelations. Following this period of upheaval they believe we will begin a new 1,000 year cycle in which peace, enlightenment and our environmental movement take priority.
• The Olduvai cliff will begin and permanent blackouts will occur worldwide, according to "The Peak of World Oil Production and the Road To The Olduvai Gorge" by Richard C. Duncan.
• Terence McKenna's Novelty Theory claims that time is a fractal wave of increasing novelty that ends abruptly in 2012.
• Tibetan Monks specialising in remote viewing predict that divine extra-terrestrials will intervene at a point where the world's governments are about to deploy weapons of mass destruction. Adding to this, the Tibetan Monks say that the world is not ready to be destroyed and that our Earth is blessed and being saved continuously from all kinds of hazards that Mankind is not even aware of.