The Federal Digital System provided by the Government Printing Office is the fastest way to access government publications. If you are looking for the current budget, texts of congressional bills, or supreme court decisions, this is a good site to use.
The Library of Congress is in essence the nation's library and provides access to written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music that document the American experience. It is a digital record of American history and creativity.
Founded in 1846, the Smithsonian is the world's largest museum and research complex, consisting of 19 museums and galleries, the National Zoological Park and nine research facilities. This site links you not only information about "America's Attic" but to many digital resources.