FirstGov
FirstGov is an official United States government website. It offers searches of government documents and features a topic index, transactions and services for individuals and businesses, links to state and government organisations and a reference shelf.

Government Information Locator Service (GLIS)
A decentralised collection of agency-based information locators to assist in the identification and location of publicly available Federal information resources.

The Federal Web Locator
Compiled by the Villanova Center for Information Law and Policy as a single point of reference to federal government information on the World Wide Web. 

Authentication of Documents for Use Abroad
This site deals with the authentication of documents for use in foreign countries.  It includes links to various state authentication authorities in the US.

Thomas Library of Congress Server
Full text of US Bills and the Congressional Record.