Aleph Search
A directory of directories. Links to selected information rich web resources, both unspecialised and specialised, with a strong emphasis on United Kingdom based sites.
http://www.alephsearch.co.uk/

Big Search Engine Index
Directory listing hundreds of search engines, categorized, described and rated.
http://www.search-engine-index.co.uk/

Search Tools for Web Sites and Intranets
Provides information, news and advice about web site searching technology. Includes a guide, search tools list, glossary, and opportunity to compare searches of its own site by different tools. Offers a free monthly email newsletter.
http://www.searchtools.com/

Search Engine Watch
A guide to search engine marketing and search engine optimization. Forums, reviews, articles, ratings, and frequent newsletters. Paying members receive access to extra content.
http://searchenginewatch.com/

Geniusfind
Categorizes thousands of the most useful topic-specific directories and databases, with descriptions.
http://www.geniusfind.com/

Direct Search
Gary Price's compilation of links to the search interfaces of resources that contain data not easily or entirely searchable/accessible from general search tools.
http://www.freepint.com/gary/direct.htm

Searchenginez
Search forms for the most effective engines in dozens of categories from Robert Skelton. Includes reviews, ratings, webmaster tools, and tutorials.
http://searchenginez.com/

FinderSeeker
Find the search engine you want by selecting a thematical category and/or country, or search by keyword.
http://www.finderseeker.com/

Fetchfido
A graphical interface of links to search engines. Multi-layered, with universal, United Kingdom, United States, European and worldwide sections.
http://homepage.ntlworld.com/fetchfido2/interface/search_engines_universal.htm

ISEDB
A directory of search engines and directories worldwide, organized by geographical area and subject, includes articles on site submission, marketing, and optimization.
http://www.isedb.com/

Pandia Powersearch
List of search engines and directories. Also includes a metasearch engine, search tutorial, and a free newsletter.
http://www.pandia.com/powersearch/

Search Engines Worldwide
Search engines sorted by geographical location.
http://home.inter.net/takakuwa/search/

Search Engine Relationship Chart
Bruce Clay's pictorial view of how search engines provide data to partner engines and directories.
http://www.bruceclay.com/searchenginechart.pdf

Complete Planet
Directory of databases and specialty search engines from Bright Planet.
http://www.completeplanet.com/

Search Engine Colossus
Directory of hundreds of search engines, organised by country and topic.
http://www.searchenginecolossus.com/

Search Engine Showdown
A user's guide to Web searching with features, comparative analysis, strategies, discussion, news and reviews.
http://www.searchengineshowdown.com/

The Ultimate Search Engine Links Page
A directory of search engines: general, metasearch, pay-per-click, children's, subject, country and people search. All are described and can be rated.
http://www.searchenginelinks.co.uk/

Indexing the Internet
An essay by John Hubbard analyzing the question of what is the best way to index the Internet, with references.
http://www.tk421.net/essays/babel.html

FTP Search Engines
Rated links to ftp and mp3 search sites.
http://www.ftpsearchengines.com/

Those Dark Hiding Places: The Invisible Web Revealed
Librarian Robert J. Lackie provides annotated links to directories, searchable sites, databases, and search engines useful for uncovering content that the general search engines fail to disclose.
http://www.robertlackie.com/invisible/index.html

Topix: Search Engines News
News on the search engine industry continually updated from thousands of sources around the Net.
http://www.topix.com/business/search-engines

OpenSearch
A collection of simple formats for the sharing of search results. Includes specifications and frequently asked questions.
http://www.opensearch.org/

Alt Search Engines
Charles Knight maintains a list of the top 100 alternative and niche search engines. Includes news, reviews and debates on search engines.
http://altsearchengines.com/

CyberTimes Navigator
The starting point that New York Times reporters and editors use for their explorations of the Web. A straightforward list of some of the best sources on the Web for all types of information.
http://topics.nytimes.com/top/news/technology/cybertimesnavigator/