Regarding internet hype, my best advice is to avoid the internet when researching 2012. The subject has attracted doomsayers, end-of-the-world armegeddonists, occultists, and just plain misinformed kooks. Many of these websites exist not to give credible and real information but to make money as most websites do by attracting sponsors. There exists only one credible author who has devoted the last decade into researching the Mayan culture and calendars. John Major Jenkins. If you are interested in learning the facts regarding 2012, this is your starting point.
The long-count calendar was one based upon the 26,000 year precession of Earth's axial wobble. Contrary to another answer on this page, the Mayans were some of the greatest astronomers and mathematicians to have lived. They divided the 26,000 year precessional cycle into 5 Ages of about 5,125 years each. This is the age which comes to an end 2012. This is not the end of their calendar any more than our calendar ends in 2007. In 2013, the next Age begins and will last 5,125 years in the same way that our Gregorian calendar will go to 2008. The Mayan calendar is further subdivided into tuns, baktuns, etc the same as we divide ours into months and weeks.
I have yet to find out why the Mayan divided the procession into 5 instead of what would seem to be a more logical 4. Their only "prediction" is that each of these ages ends in a certain way. The age we are now in is called the age of the jaguar. When the jaguar dies, it's body will shiver and quake. This would be a referrence to the Earth experiencing earthquakes and possibly volcanic activity. This is the only Mayan prediction. All others are false and have been made up during the last ten years by people living today to assert fear and confusion. Mayans have never spoke of any age as the 'end of the world' as unfortunately most people assume. They only spoke of the ending of an age as a time of transition. This is what is the cause of so much of the confusion and scare-hype happening on the internet these days. 2012 has absolutely nothing to do with asteroids or polarity flips.
The Mayan were aware of naturally occuring cycles. The age that ended 3114BC was the age of water. Documented evidence does not exist but one could suppose that that may have been the time of the Biblical flood which is also spoken of in many other cultures of the globe. We know that previous civilizations have existed in the far past yet we have very little in the form of historical documents that go much beyond the last 2000 years. Information does not even exist about the building of the Egyptian pyramids or the Sphinx. One could presume that the demise of these previous civilizations were possibly caused by global catastrophes.
Clearly, the last set of humans did survive otherwise you and I would not be here today. Exactly what happened at the ends of the other ages will probably never be known. Nor the percentage of humans that died or survived. Possibly 26,000 years from now the records of today may still exist. But who can say?
I am not a scientist. I am just trying to give people proper education regarding a subject which unfortunately has become so twisted and mangled with misinformation and lies. This is an astronomical event which occurs only once every 26,000 years. Look forward to it with admiration and respect, not fear.