December 3, 1984: The Bhopal Disaster kills thousands in India.
December 3, 1967: In Cape Town, South Africa, a transplant team headed by Christiaan Barnard carries out the first heart transplant on a human (53-year-old Louis Washkansky).
December 3, 1926: Agatha Christie disappearsafter kissing her daughter goodnight and driving off into the darkness. A national search ensues. Finally after 11 days, Christie is discovered living in a hotel under a false name, that of her husband’s mistress.
There’s a Straight Dope column on that.
December 3, 1586: Sir Thomas Herriot introduces potatoes to England from Colombia.
December 5, 1945: 5 navy bombers carrying 14 men disappear over the Bermuda Triangle. The rescue aircraft sent out after them also disappears with its crew of 13. No traces have ever been found.
December 5, 1952: The “Great Smog”: A cold fog descends upon London, combining with air pollution, and killing at least 12,000 in the weeks and months that follow.
December 6, 1917: The Halifax Explosion. A French ship SS Mont-Blanc, laden with explosives for the war, collides with another ship leading to the largest single manmade explosion ever prior to the development of nuclear weapons. 2000 die, 9000 are injured and much of the city of Halifax, Nova Scotia is destroyed. Because the ships burned for some time before the large detonation, many onlookers were watching unaware of the horror that was coming. Of the 9000+ injured, over 1000 were immediately blinded by the blast.
December 5, 1933: The 21st Amendment to the US Constitution is ratified, repealing the 18th Amendment (Prohibition).
EDIT: Still the 5th here in Hawaii.
December 6, 1865: The Thirteenth Amendment to the United States Constitution is ratified, banning slavery.
December 6, 1989: The Ecole Polytechnique massacreoccurs when a lone gunman kills 14 women in Montreal.
(in addition to the obvious anniversary)
December 7, 1930: W1XAV in Boston telecasts video from the CBS radio orchestra program, The Fox Trappers. The telecast also includes the first television commercial in the United States, an advertisement for I.J. Fox Furriers, who sponsored the radio show.
December 8, 1980: John Lennon is murdered.
December 8, 1813: Premiere of Beethoven’s Seventh Symphony, conducted by Beethoven himself. The piece was very well received, and the second movement, the Allegretto, had to be encored immediately.
December 9, 1967: Nicolae Ceaușescu becomes president of Romania (to be overthrown 22 years later).
December 10, 1684: Isaac Newton’s derivation of Kepler’s laws from his theory of gravity, contained in the paper De motu corporum in gyrum, is read to the Royal Society by Edmond Halley.
December 10, 1964 - Dr. Martin Luther King, Jr., received the Nobel Peace Prize.
December 10, 1799: The metric system is adopted in France, the first country to do so.
December 11, 1941: Germany and Italy declare war on the United States, following the Americans’ declaration of war on the Empire of Japan in the wake of the attack on Pearl Harbor.
December 11, 1282: After a 23-year reign, Llywelyn ab Gruffydd (Llywelyn the Last), the last native Prince of Wales, is killed at Cilmeri, near Builth Wells in southern Wales.
December 12, 1935: Lebensborn Project, a Nazi reproduction program, is founded by Heinrich Himmler.