Huge banner headline in the (left-of-center) Guardian today: 100,000 Iraqi civilians dead, says study. The study to which it refers was published by the Lancet, Britain's most respected (and peer reviewed) medical journal. It used sampling, but looks serious.
Although some of the casualties are due to things like an increase in infant mortality because women are unable or too frightened to go to hospitals to deliver, the great bulk of the deaths is civilians killed by aircraft bombings or helicopter-launched munitions.
The amount of civilian casualties is sufficiently high to call into question whether the US has complied with the (rather vague) laws of humanitarian warfare.
Update (10/30): Slate has a good article noting the gigantic margin of error admitted by the authors of the report — so large as to call into question their publicizing the midpoint of a range of possibilities from 8,000 to almost 200,000.