This report is from DemocracyNow.org:

A new report by the Congressional Budget Office estimates the US will have spent $100 billion by the end of the year on private contractors in Iraq since the invasion in 2003. The Pentagon’s reliance on outside contractors in Iraq is proportionately far larger than in any previous conflict. The Washington Post reports contractors in Iraq now employ at least 180,000 people in the country, forming what amounts to a second private army, larger than the United States military force.

Here’s additional information from the NYT, which reports that, according to the CBO report, this amount of private contracting “reflects the Bush administration’s unprecedented level of dependence on private firms for help in the war”