Today (10th August 2008) is Tisha b'Av (the 9th Day of the Hebrew Month of Av), a day of mourning and fasting during which we commemorate the destruction of the Holy Temple, which happened not once but twice on this day in history.
Other destructive events which occured on 9 Av include: the fall of Betar, the last fortress to hold out against the Romans during the Bar Kochba revolt in 132 CE, killing 100,000 Jews. In 1492, Spain ordered the expulsion of all Jews by the Ninth of Av. In 1914, Germany declared war on Russia on the Ninth of Av (August 1) which was the beginning of World War I, the event that led to WWII and the Holocaust.
Read more: Tisha b'Av on Har HaBayet - The Temple Mount IS In Our Hands!