"Freedom of Information (FOI) Day is an annual event on March 16, the birthday of James Madison, who is widely regarded as the Father of the Constitution and the foremost advocate for openness in government" - ALA.org
Congress.gov provides access to federal legislative information. You can find current legislative activities (including live video feeds), committee reports, bill texts, congressional records, information about house representatives and senators (like bills they've sponsored!) more.
USA.gov is the official US government web portal and provides information about programs and services, government agencies, elected officials, and numerous other useful items.
MetaLib searches multiple US Federal databases to retrieve articles, reports, and other information. This aggregates searches to databases like the Library of Congress, FDSys, USA.gov, PubMed, and more.
Sometimes you need to physically go to a depository. This directory will help you locate local ones. Local ones include Slippery Rock, Pittsburgh, and New Castle.
Open access government data sets for everything agricultural crop yields to lending data to higher education and health care.
The official National Archives site with archival data related to immigration to research ancestry, military records, cartographic records, and more.
FDsys provides free online access to government executive, legislative and judicial reports and other publications.
No list of government resources is complete without the Census Bureau. The resources related to census data are countless.
Repository of over 500000 serials, congressional publications, eBooks, and more.