The following resources represent the cooperative efforts of multiple governmental agencies.
FedWorld: is a gateway to government information. [The] site is managed by the National Technical Information Service (NTIS) as part of its information management mandate.
FDSys: was discontinued on 12/14/2018. The information contained therein is now available at govinfo.gov.
govinfo.gov: is a service of the United States Government Publishing Office (GPO), which is a Federal agency in the legislative branch; it provides free public access to official publications from all three branches of the Federal Government.
USA.gov: (fka FirstGov) is an interagency initiative administered by the U.S. General Services Administration's Office of Citizen Services. It got its start when Internet entrepreneur Eric Brewer, whose early research was funded by the Department of Defense, offered to donate a powerful search engine to government.