The Catalog is the finding tool for federal publications that includes descriptive information for historical and current publications as well as direct links to the full document, when available. Users can search by authoring agency, title, subject, and general keywords, or click on "Advanced Search" for more options.

DiscoverGov provides simple, one-stop searching across multiple U.S. Federal Government databases including GPO's Catalog of U.S. Government Publications (CGP) and GovInfo.

GovInfo provides free public access to official publications from all three branches of the Federal Government. Coverage is strongest from the mid 1990s onwards, but older documents can be found here as well. New content is added daily. Use this database to find the text of legislation, bills, etc.

MetaLib is a federated search engine that searches multiple U.S. Federal government databases, retrieving reports, articles, and citations while providing direct links to selected resources available online. MetaLib is a service of the Catalog of U.S. Government Publications (CGP).

This is almost certainly the most comprehensive database of Congressional publications, some dating back as far as the late 1700's. Includes the complete texts of hearings and most other documents. An interesting sub-set of the database provides legislative histories. (Law Library subscription.)