INTERNET SEARCHENGINES (General)

Google
Largest database of webpages

Yahoo!
Popular search engine and subject directory

Bing
Popular search engine run by Microsoft

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

SCIRUS
 Scientific research search engine - includes links to journal articles, as well as to scientists' homepages, courseware, institutional repositories and other related websites

Search.USA.gov
U.S. government's official search engine - includes information from federal, state, local, territorial and tribal websites

SUBJECT DIRECTORIES (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

Best Information on the Net (St. Ambrose University Library)
Online sources organized by academic major, popular paper topic, or alphabetical order

Complete Planet
 Search engine and web directory, retrieves records through both databases and search engines and locates "deep web" records difficult to find through other search engines

INFOMINE
 Virtual library of university-level internet resources, created by librarians and researchers

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)

Open Directory Project
 Largest human-edited web directory, created and maintained by volunteer editors across the globe

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