We have discussed mainly three categories of search tools 

•  Directory-based search engines 
•  Spider based search engines 
•  Meta Search Engines

These general-purpose tools are usually sufficient for routine searches. However for complex or focused searches, you need more specialsed tools.

As case study, we discussed resources on business directory search last week and reviewed more than 30 directories on India and a few select world directories. This week we review more resources on special search engines.

•  SearchAbility An overview of specialised search engines: http://www.searchability.com/
• BigHub It lets you search for a subject-specific search engine by keyword or category. It also doubles as a worthy metasearch engine. http://www.thebighub.com/
• Lookoff "Lookoff is not a search engine, but rather searches for specific and topical search engines" http://www.lookoff.com
• Europe: Search Europe http://searcheurope.com 
• Euroguide http://www.euroguide.org/euroguide/subject-listing/

Search Engine of Search Engines

• FinderSeeker : Search engine for search engines http://www.finderseeker.com/
• Search Engine Colossus: International Directory of search engines http://www.searchenginecolossus.com/
• Phil Bradley's list Country search engines and regional search engines - currently a total of 1,517 search engines and 169 countries and regions http://www.philb.com/countryse.htm
• European Search Engines, Directories and Lists http://www.netmasters.co.uk/european_search_engines/
• Search Engines Worldwide http://www.twics.com/~takakuwa/search/search.html

Reference library (Factual information)

• XRefer - The Web's reference engine http://www.xrefer.com/
• iTools - Quick access to the best Internet tools http://www.itools.com/

Person Search

• Bigfoot http://bigfoot.com/
• Infospace http://www.infospace.com/
• WhoWhere http://www.whowhere.lycos.com/
• AnyWho http://www.anywho.com/
• Nedsite http://www.nedsite.nl/search/people.htm
• WED - World e-mail directory http://worldemail.com/

Software Downloads

• CNET's Download.com http://download.cnet.com/
• ZDNet Downloads http://www.zdnet.com/downloads/
• WWW.32bit.com http://www.32bit.com/
• TUCOWS http://tucows.wau.nl/ 
•  CGI Resources - Probably the Web's best source for CGI programs http://cgi.resourceindex.com/
• Script Search http://www.scriptsearch.com/
• PHP Resources - Over 800 PHP related resources in more than 190 categories http://php.resourceindex.com/