CRS is a non-partisan research service for Congress that produces highly regarded reports on legislative and policy issues at the request of Congress. These are excellent sources, written by experts, for getting background on major legislation, foreign policy issues, etc.
Online access to Congressional Quarterly pubications: Congress and the Nation; Historic Documents; Politics in America; and five CQ Guides: Guide to Congress; Guide to the Presidency; Guide to the U.S. Supreme Court; Guide to U.S. Elections; Guide to Political Campaigns in America.
Opposing Viewpoints covers current controversies and hot topics. It features viewpoint articles, topic overviews, full-text magazine, academic journal, and newspaper articles, primary source documents, statistics, images and podcasts, and links to Websites.
Joint effort between UT-Austin, Penn State, U Washington funded by the NSF. The project tracks policy changes in the United States. It 'collects and organizes data from various archived sources to trace changes in the national policy agenda and public policy outcomes since the Second World War.'
"Non-profit institution that helps improve policy and decisionmaking through research and analysis." Focuses on health, education, national security, international affairs, law and business, the environment, and more.
Independent, federally-funded national security institution. Includes full-text of peace agreements; documents on inter- and intra-state conflicts; and documents on truth commissions (see the Library link) and links to websites on foreign affairs topics such as terrorism, human rights, peacekeeping, etc.