National Technical Information Service - The National Technical Information Service provides innovative data services to federal agencies, through joint venture partnerships with the private sector, to advance federal data priorities, promote economic growth, and enable operational excellence.
Gov Engine - directory of Federal, State, and Local Government as well as Court links
Science Gov - gateway to authoritative, selected science information provided by U.S. government agencies
USA Gov - Whatever you want or need from the U.S. government, it's here; a rich treasure of online information, services, and resources. Overwhelming amount of information. Try the directories - searching these is usually more direct than results from the general search box. Also try the FAQs, a huge number of questions (over 2,000) so someone might already have asked your question. Formerly called First Gov.
Congress.gov The official website for U.S. federal legislative information. The site provides access to accurate, timely, and complete legislative information for Members of Congress, legislative agencies, and the public. It is presented by the Library of Congress (LOC) using data from the Office of the Clerk of the U.S. House of Representatives, the Office of the Secretary of the Senate, the Government Publishing Office, Congressional Budget Office, and the LOC's Congressional Research Service.
USAJOBS.gov The Federal government's official job list. Includes employment search, information center, veteran information and forms.
American Fact Finder - provided by the U.S. Census Bureau; includes a population clock
United States House of Representatives - Offical website for the U.S.House of Representatives
United States Senate - Offical website for the U.S. Senate
All federal, city, state or international governmental agencies offer great resources of free, reliable and authoritative material. The selected links in this guide offer some of the best and most popular government sites.
Census Atlas of the United States - with more than 700 full-color maps, this is the first general population and housing statistical atlas published by the Census Bureau since 1925!
GPO Access. A service of the Government Printing Office that provides free electronic access to an enormous amount of important information produced by the Federal Government.
Contacting the Congress - Congress information including committee membership, biographies, fax numbers and email addresses of Senators and Representatives. Search by state and zip code
State and County Quick Facts - US Census Bureau provides statistics for all states and counties, and for cities and towns with a population of 5,000
Federal Tax Forms. It's not too early to start thinking about April 15th. Provides lots of FAQs and guidance on various tax issues for individuals. Tab at the toop of page for "forms"
Government Publishing Office The U.S. Government Publishing Office (GPO) is the Federal Government’s official, digital, secure resource for producing, procuring, cataloging, indexing, authenticating, disseminating, and preserving the official information products of the U.S. Government.
Historical Statistics of the United States, Colonial Times to 1970 - PDF, very large file which takes some time to load
Statistical Abstract of the United States (1900-2012) from the US Census Bureau published since 1978, the authoritative and comprehensive summary of statistics on social, political, and economic organizations of the US.
Web Guide to U.S. Supreme Court Research - not a government guide, but created by a law librarian. This guide is for both the beginner and hardcore researcher. An acclaimed site.