American Memory: Historical Collections for the National Digital Library: American Memory is a gateway to the Library of Congress' rich primary source materials relating to the history and culture of the United States. The site offers millions of digital items - text, images and audio files - from the Library's vast historical collections.
ERIC: The U.S. Department of Education's database of education literature.
GPO Access: The Government Printing Office's gateway to Federal publications and documents.
GrayLit Network - A Science Portal of Technical Reports: Makes available Federal agencies' gray literature. ("Gray literature" refers to open source material that is available through specialized channels and may not enter the usual systems of publication and distribution.)
PubMed: The National Library of Medicine's free search service to over 16 million citations on the Medline and Pre-Medline databases.
OSTI: From the US Department of Energy's Office of Scientific and Technical Information (OSTI), as part of their mission to advance science and sustain technological creativity by making R&D findings available and useful to Department of Energy (DOE) researchers and the American people. Also visit the DOE Information Bridge for full-text DOE Report literature and the E-Print Network for a "one-stop shopping" site for preprints in science and technology. OSTI is a component of EnergyFiles Virtual Library Collection of Energy Science and Technology.