Here is a link to an article originally published in a 1995 issue of Mountain Astrologer. It gives a  summary of how the different Maya calendars combine to give the "end date" of when the Maya believe time will "start over" on `12/21/12.

http://www.levity.com/eschaton/Why2012.html

This is a link to a website that has interesting information on event that can be 'claimed' to have been accurately predicted by different astrological research and patterns.

http://internet.cybermesa.com/~jasm/