This has been in the news for a couple of days now, but Juan Cole at Informed Comment posted what, to me, is the most horrifying bit of information thus far:
"Some 80 bodies have been found in Baghdad and environs since Monday. On Tuesday alone, police discovered 46 bodies around the capital. They appear mostly to have been Sunni Arabs targeted by enraged Shiites attacked by the guerrillas during the past three weeks. Some were in the back of a minibus. Some were in a mass grave in Shiite East Baghdad. The latter were discovered when passers-by saw blood oozing out of the earth. Blood oozing out of the earth is a good metaphor for Iraq nowadays."