Lewis & Clark Libraries: Reference Shelf: Start Here

OED

The O.E.D. provides authoritative definitions and traces the usage of words from their first recorded occurrence to the modern period.

Britannica Online
Online edition of the Encyclopaedia Britannica. Includes a dictionary and thesaurus.

Encyclopaedia Britannica Online includes the complete encyclopedia, with more than 101,000 articles and thousands of media entries, including charts, photographs, drawings, maps, flags, and more. Also included are Merriam-Webster's Collegiate Dictionary and Thesaurus, Britannica Student Encyclopedia, and Notable Quotations, plus links to magazine and journal articles via EBSCO and to outside websites selected by Britannica editors.
Gale Virtual Reference Library
A collection of full-text, multi-volume reference titles in a range of subject areas.
Oxford Reference Online
Electronic version of Oxford reference across a broad range of topics. Full-text.
Columbia Gazetteer of the World
A comprehensive encyclopedia of geographical places and features.