Tu B'Shevat, the Jewish New Year of Trees, begins today at sundown and ends at sundown tomorrow. The holiday takes its name from its date on the Hebrew calendar, with 'Tu' referring to the 15th, and 'Shevat' being the 11th month of the Jewish calendar.
To learn more about the customs and history of Tu B'Shavat check out the following links:
http://en.wikipedia.org/wiki/Tu_BiShvat
http://www.jewfaq.org/holiday8.htm
http://www.joi.org/celebrate/tubshevat/index.shtml
http://www.reformjudaism.org/tu-bishvat-history
http://www.chabad.org/library/article_cdo/aid/3264/jewish/Tu-BShevat.htm