I've been investigating the significance of December 21, 2012 for quite some time. One of the best explanations I've found is contained in the following film (divided into in 11 short video clips). Many of the foremost researchers into the Mayan calendar end date offer succinct explanations of their findings. The complete set of video clips can be found at And You And I.
Gregg Braden - 2012 Shift of the Ages (1/11)
Gregg Braden - 2012 Shift of the Ages (2/11)
Gregg Braden - 2012 Shift of the Ages (3/11)
Gregg Braden - 2012 Shift of the Ages (4/11)
Gregg Braden - 2012 Shift of the Ages (5/11)
Gregg Braden - 2012 Shift of the Ages (6/11)
Gregg Braden - 2012 Shift of the Ages (7/11)
Gregg Braden - 2012 Shift of the Ages (8/11)
Gregg Braden - 2012 Shift of the Ages (9/11)
Gregg Braden - 2012 Shift of the Ages (10/11)
Gregg Braden - 2012 Shift of the Ages (11/11)
Gregg Braden - 2012 Shift of the Ages (2/11)
Gregg Braden - 2012 Shift of the Ages (3/11)
Gregg Braden - 2012 Shift of the Ages (4/11)
Gregg Braden - 2012 Shift of the Ages (5/11)
Gregg Braden - 2012 Shift of the Ages (6/11)
Gregg Braden - 2012 Shift of the Ages (7/11)
Gregg Braden - 2012 Shift of the Ages (8/11)
Gregg Braden - 2012 Shift of the Ages (9/11)
Gregg Braden - 2012 Shift of the Ages (10/11)
Gregg Braden - 2012 Shift of the Ages (11/11)