Library of Congress

The Library of Congress has a wealth of information, including their on-line catalog and a number of other institutions through a "Z.39.50" gateway as one of their "Library Services." They also offer an extensive set of links to other resources (the economics-oriented ones are generally described elsewhere here) and substantial information on the U.S. Government, including Congress. It appears one can use their photocopy service long distance.

http://www.loc.gov