USA.gov is the United States Government's offical website for all government transactions, services, and information. You can learn how to apply for a passport, replace personal records, find government agencies (courtesy of the A-Z Index of the United States Government), and find out how to contact agency and elected officials.
Govinfois a service of the Government Printing Office. Govinfo contains "America's Authentic Government Information," according to the website. Featured collections include the U.S. Government budget, Code of Federal Regulations, Compilation of Presidential Documents, Congressional Bills, Documents, and Hearings, just to name a few.
Regulations.gov allows citizens to let their voices be heard in federal decision-making. You can search for administrative rules, comments, adjudications, supporting documents, and leave your own comment on a notice of proposed rulemaking!