The Mayans never claimed that 2012 marked the end of the world, that's just when the calendar ended. They created their calendar based on solar and other astronomical alignments.
Nostradamus studied the Mayans and their works and he pretty much popularized the world ending in 2012 business. Most of Nostradamus' works were total crap, and this is falls under the same category.
But going back to the Mayans, their calender is pretty amazing. The fact that an ancient civilization could understand complicated cycles of our galaxy without satellites and telescopes is bizarre. Their calender ends on December 21st, 2012, which is an approximate for when their December solstice sun aligns with the galactic equator.
And all of you guys relating it to the Bible are idiots, the Bible never mentions 2012, world war 3, or pretty much anything in this thread.