Check out GPO’s MetaLib:
“Welcome to MetaLib, a service of the Catalog of U.S. Government Publications! MetaLib is a federated search engine that searches multiple U.S. Federal government databases, retrieving reports, articles, and citations while providing direct links to selected resources available online. To learn more, view additional brief or detailed search information.” (Link to Metalib homepage.)
To learn more about GPO (the Government Printing Office), link to their homepage and to FDSys, the Federal Digital System, and don’t forget visiting their award winning Government Book Talk Blog.
Read about federated searching at Wikipedia and here and here and here.
(Thank you to Notabeneuh blog: GPO Launches MetaLib for the lead.)