U.S. General Accounting Office - congressional investigative agency that examines the use of public funds, evaluates federal programs and activities, and provides analyses, options, recommendations, and other assistance to help the Congress make effective oversight, policy, and funding decisions.
Fedstats - statistics from federal agencies, available broken down geographically, by agency, or in other forms.
National Governors' Association - site includes updates on key policy and legislative priorities, many of which are influenced by federal budget appropriations.
National Priorities Project - examines federal budget priorities and impacts on states and local communities.
The Concord Coalition - "nonpartisan, grassroots organization dedicated to eliminating federal budget deficits and ensuring Social Security, Medicare, and Medicaid are secure for all generations."