2012 and the Mayan Long Count Calendar

According to the Popol Vuh, a book compiling details of creation
accounts known to the K'iche' Maya of the Colonial-era highlands,
we are living in the fourth world. The Popol Vuh describes the first
three creations that the gods failed in making and the creation of the
successful fourth world where men were placed. In the Maya Long
Count, the previous creation ended at the start of a 13th b'ak'tun.

The previous creation ended on a long count of 12.19.19.17.19.
Another 12.19.19.17.19 will occur on December 20, 2012, followed
by the start of the fourteenth b'ak'tun, 13.0.0.0.0, on December 21,
2012.

Significance within the New Age movement

Three figures within the New Age, the artist and theorist José
Argüelles, John Major Jenkins, and the late ethnobotanist and
psychonaut Terence McKenna, have publicized theories concerning
the significance of the end of the cycle. (They arrived at their
conclusions separately from one another). They have jointly inspired
a number of articles and books that this will be the end of this
creation, the next pole shift or, as McKenna speculated in his
theories, the end of history and events as "novel" as the origin of life
on Earth, which we could not possibly imagine. Jenkins has
focused on the occurance of a Galactic Alignment in the "era of
2012". Other, more mundane speculations involve a worldwide
catastrophe, such as a pole shift. The idea of the significance of the
date has also increasingly passed into popular culture