[Updated to correct some typographical errors and to add more information.]
Major news today is that terrorist gunmen shot at least 12 people dead at the Paris offices of the satirical newspaper Charlie Hebdo (Charlie Weekly), which had come under criticism for publishing cartoons of the prophet Muhammad. Catherine Thompson at Talking Points Memo has a reasonably brief background report on the newspaper that's worth a quick read (link).
In brief, the paper is known for attacking and ridiculing everybody, and a number of its cartoons about Muhammad have provoked diplomatic problems between France and Islamic countries and threats against the newspaper, whose previous offices were fire-bombed. A particularly offensive cartoon, showing Muhammad bending over with his genitals exposed, was widely criticized around the world, including by the French and U.S. governments, though both governments also defended the newspaper's right to print things even when doing so seems tasteless and stupid.
The paper also publishes things that offend Christians and especially Catholics, but this has apparently not led to any notable threats or violence.
Update: As you almost certainly know, the French authorities believe they have identified the attackers, and the reaction from around the world, including in Egypt and other parts of the Muslim world, has been strongly in support of press freedoms and the victims. The BBC website has a report on the suspects (link), on public demonstrations of mourning and solidarity (link), and on the responses of cartoonists in France and abroad (link). The two main symbols of defiance against the terrorist attack are pens (symbolizing writing and drawing) and signs reading "Je suis Charlie" ("I am Charlie").