Much has been written about December 21, 2012 and the end of the Mayan calendar. Most people recognize that it does not mark the end of the world, but rather the disintegration of outmoded ways of thinking and the beginning of a new heart-centered consciousness. It is a gradual process.
"Galactic alignment" is a term that many people are using to try to identify the cause of this change in consciousness. To better understand what's happening, here's a short primer on astronomical events related to December 21, 2012...
The sun (and earth) last crossed the galactic plane 3 million years ago and is moving away from the galactic plane. It will take another 30 million years to cross it again. So the significance of December 21, 2012 has nothing to do with the earth or sun crossing the galactic plane.
(The above image is from the Santa Barbara Museum of Natural History.)
By definition, the sun is always on the galactic equator. Since our solar system is at a 60 degree angle to the galactic equator, in its orbit, the earth crosses the galactic equator twice every year at approximately the summer and winter solstices. So there's nothing unique about the earth crossing the galactic equator.
On December 21, 1998 the earth (and the sun) was precisely on the galactic equator. The sun is approximately 1/2 degree wide in the sky. As seen from the earth, each year on Dec 21 from 1980 to 2016 the sun will be "touching" the galactic equator (36 years), but only for a few days surrounding December 21st (and also near June 21st). So it's not likely the Mayans were thinking this was the signature reason to reset the entire calendar on December 21, 2012.
This explanation from Thomas Razzeto makes more sense. On December 21, 2012, the sun, as seen from the earth, is directly in the dark rift of the Milky Way, which is slightly off the galactic equator. Thus we have the winter solstice and the sun coming out of the birth canal. In addition, the Mayan are in Central Time Zone, so the solstice will be just before sunrise (the third rebirth of the sun).
(The above image is from an essay by Thomas Razzeto.)
We are entering into a new stage of consciousness but do not become discouraged if December 22nd looks a lot like December 21st. Many astronomical explanations erroneously imply this will be a sudden change (possibly with accompanying pole shifts and other wild scenarios).
During this period of "unknowing" the important thing is to remain centered and to focus on all the good things in your life that you can be thankful for. In other words, live this day like any other day in which you'd like to feel joyous and fulfilled. Happy December 21st!