E-journals

• List of Free Ejournals from the Smithsonian Institution Libraries
• Highwire Press (access is free except for the most recent content)
• BioMedCentral (access is free for most content)
• AGORA

Bibliographic databases

• List of Index Databases from the AMNH Library (free titles are indicated with this icon:  )
• Citation and Full Text Databases from the Smithsonian Institution Libraries (free titles are indicated)
• Google Scholar (provides a way to search for journal articles on a topic; searches sometimes result in links to free articles)

E-books

• IUCN Catalog of Publications has links to full-text books and reports
• Project Gutenberg
• Science section of Online Books Page from University of Pennsylvania
• National Academies Press (allows access to many titles for free --but not for downloading)

Reference materials

• Smithsonian Institution Libraries Reference Shelf
• Librarians' Index to the Internet - Ready Reference and Quick Facts
• LibrarySpot Reference Desk (see the menu on left of the page)
• AcademicInfo Online Subject Guides

Useful Internet portals

• Natural History: Guides to the Web/Portals from the Smithsonian Institution
• Natural History Reference Sources compiled by Adam Schiff at the University of Washington
• Librarians' Index to the Internet Science Listings

Mapping information

• Atlases, Gazetteers, GIS and Maps from the Smithsonian Institution
• Geographic Names Information System (GNIS)
• Perry-Castañeda Library Map Collection