CBO's report on the costs of US operations in Iraq, Afghanistan and other related activities (CBO Testimony) states that overall expenditures exceed 600 billion dollars. Their analysis also includes expenditures which aren't explicitly budgeted for this purpose such as Veteran's Administration expenditures.

New from the Miller Center at the University of Virginia is the official web site for the National War Powers Commission.

In keeping with its tradition of assembling national commissions of major stature, the Miller Center has convened the National War Powers Commission, a private bipartisan panel led by former Secretaries of State James A. Baker, III and Warren Christopher. The Commission will examine how the Constitution allocates the powers of beginning, conducting, and ending war.

Here's the official press release announcing the commission.
PDF; 2 pages.