"A quick and ready reference for United States Attorneys, Assistant United States Attorneys, and Department attorneys responsible for the prosecution of violations of federal law. It contains general policies and some procedures relevant to the work of the United States Attorneys' offices and to their relations with the legal divisions, investigative agencies, and other components within the Department of Justice."
General Accountability Office (GAO) Reports and Testimonies (1995- ) - "GAO is known as 'the investigative arm of Congress' and 'the congressional watchdog.' GAO supports the Congress in meeting its constitutional responsibilities and helps improve the performance and accountability of the federal government for the benefit of the American people." Most GAO reports are done at the request of members of Congress.
Congressional Research Service Reports (CRS Reports) - The Congressional Research Service is the research arm of the Library of Congress and provides reports to members of Congress on a variety of topics relevant to current political events. The reports are not readily accessible to the research community, but a few websites have been collecting them and making them accessible:
The Library has some CRS Reports in print. Search the catalog by author: Library of Congress Congressional Research Service.
There's also an index: A Guide to Major Studies and Issue Briefs of the Congressional Research Service (Call No.: Z1223.A1 G81, Regenstein Library, 1st Floor Reference Collection), which covers from 1916-1974.
The CQ Researcher is a collection of reports covering political and social issues, with regular reports on topics in health, international affairs, education, the environment, technology and the U.S. economy.