govinfo.gov: By GPO. It provides online access to official publications from all three branches of the U.S. federal government, including the federal budget, congressional documents, the U.S. Code, and more. Coverage will vary by collection, but many publications are available in full text back to the 1990s.
USA.gov: It is the official guide to government information and services. It can help you start your search for government information by topic and agency. It searches across government agencies and across all geographic levels: Federal, states, local, tribe.