Government Accountability Office (GAO) - "(GAO) is an independent, nonpartisan agency that works for Congress....We provide Congress with timely information that is objective, fact-based, nonpartisan, nonideological, fair, and balanced."
Congressional Budget Office (CBO) - "(CBO) has produced independent analyses of budgetary and economic issues to support the Congressional budget process. The agency is strictly nonpartisan and conducts objective, impartial analysis, which is evident in each of the dozens of reports and hundreds of cost estimates that its economists and policy analysts produce each year."
Congressional Research Service (CRS) - "CRS is well-known for analysis that is authoritative, confidential, objective and nonpartisan. Its highest priority is to ensure that Congress has 24/7 access to the nation’s best thinking."
Current Issues, Hot Topics & Controversies - guide to library resources that are unavailable through the Free Web
IssueLab - "[P]rovide[s] free access to thousands of case studies, evaluations, white papers, and issue briefs addressing some of the world's most pressing social problems."