Tuesday, 2010 December 21 is the winter solstice in the Northern Hemisphere. After Tuesday, the days start getting slowly longer again.
This year, the solstice is marked by a total lunar eclipse which will occur on Tuesday morning. The last time a lunar eclipse and the winter solstice were on the same day was the year 1638. The next occurrence won't be until 2094 -- I have ambitions to watch it, but that is predicated on either the technological singularity occurring, or on sufficient medical advances to keep me from total decrepitude.