Listing of what is available at govinfo and links to other legislative, executive and judicial process resources. The Catalog of U.S. Government Publications (CGP), a finding tool for government publications (from July 1976 -present), includes records for print and content available on govinfo and links to govinfo for access to these publications
Think Tanks, advocacy organizations, and foundations often provide policy research reports. These can be found in databases, and on individual organization websites.