INTERNET SEARCH ENGINES

Google
Largest database of webpages

Yahoo!
Popular search engine and subject directory

Bing
Popular search engine run by Microsoft

META-SEARCH ENGINES

Meta-search engines compile and sort results from multiple search engines.

Dogpile
Meta-search engine which brings together top results from Google, Yahoo!, and Bing

AllPlus
Meta-search engine which compiles top results from search engines like Google, Yahoo!, MSN Live, and Ask.com

CONTENT-SPECIFIC SEARCH ENGINES

Google Scholar
Google's search engine for scholarly sources

SUBJECT DIRECTORIES

Subject directories are resources for specific topics.

Academic Info Online Subject Guides
Large collection of subject guides for academic disciplines and specific research topics - list both online resources and printed reference works.

Intute
Provides access to a variety of web resources for research.

Internet Public Library (IPL2)
Collections of resources from the Internet Public Library (IPL) and the Librarians' Internet Index (LII).

Virtual Reference Shelf (Library of Congress)
Selected high-quality resources for research organized by subjects and categories.