The winter solstice marks the longest night of the year, and has been celebrated in one form or another for thousands of years. Today, people who follow earth-centered religions continue to mark this holiday which celebrates the return of the light.

To learn more about the science of the winter solstice, take a look at:
http://scienceworld.wolfram.com/astronomy/WinterSolstice.html
or
http://www.oarval.org/Smdec96.htm

For a really cool site with information about celebrating the solstice, try:
http://www.candlegrove.com/solstice.html
or
http://www.circlesanctuary.org/pholidays/WinterSolstice.html
On this site, make sure to check out link for Winter Solstice Celebrations for Families and Households, and the recipe for Wintertime Wassail (spiced hot cider).