GPO just released MetaLib, a federated search engine for U.S. government publications. (“Federated” means that it simultaneous multiple databases, and presents you with a set of results for each). MetaLib searches 53 sources, including the Catalog of U.S. Government Publications, Library of Congress, usa.gov, and numerous agency sites. For more information, see GPO’s official announcement.
For anyone doing research involving government documents, it would be interesting to test MetaLib against Uncle Sam Google….