General search engines

Alexa Internet
Ask.com (formerly Ask Jeeves)
Baidu
Exalead
Gigablast
Google
Live Search (formerly MSN Search)
MozDex
WiseNut
Yahoo! Search

Open source search engines

DataparkSearch
Egothor
Gonzui
Grub
Ht://dig
Lucene
Lemur Toolkit & Indri Search Engine
mnoGoSearch
Namazu
Nutch
OpenFTS
Sphinx
SWISH-E
Terrier Search Engine
Wikiasari
Xapian
YaCy
Zettair

Meta search engines

Bioinformatic_Harvester
Brainboost
Clusty
Dogpile
Excite
HotBot
Info.com
Ixquick
Mamma
Metacrawler
MetaLib
Myriad Search
PolyMeta
SideStep
Turbo10
WebCrawler

Regional search engines

Accoona, China/US
Alleba, Philippines
Ansearch, Australia/US/UK/NZ
Araby, Middle East
Baidu, China
Daum, Korea
Guruji.com, India
Miner.hu, Hungary
Najdi.si, Slovenia
Naver, Korea
Rambler, Russia
Rediff, India
SAPO, Portugal
Search.ch, Switzerland
Walla!, Israel
Yandex, Russia

People search engines

ZoomInfo

Email-based search engines

TEK

Visual search engines

Grokker
Kartoo
Quintura

Answer-based search engines

Answers.com
AskMeNow
BrainBoost
Lexxe
Lycos iQ
Windows Live QnA
Yahoo! Answers
eHow

Google-based search engines

AOL Search
MySpace Search
Mahalo.com
Netscape
CompuServe Search

Yahoo!-based search engines

AltaVista
AlltheWeb
GoodSearch

Windows-Live-based search engines

A9.com

Ask.com-based search engines

Lycos

Job search engines

Naukri.com (India)
Bixee.com (India)
Craigslist (by city)
Eluta.ca (Canada)
CareerBuilder.com (USA)
Hotjobs.com (USA)
Indeed.com (USA)
Monster.com (USA)
Recruit.net (International)
SimplyHired.com (USA)

Forum search engines

Omgili

Blog search engines

Amatomu
Bloglines
BlogScope
IceRocket
Sphere
Technorati

News search engines

Google News
MagPortal
Newslookup
Nexis (Lexis Nexis)
Topix.net
Yahoo! News

Multimedia search engines

blinkx
Picsearch
Podscope

Code search engines

Google Code Search
JExamples
Koders
Krugle

BitTorrent search engines

These search engines work across the BitTorrent protocol.

Btjunkie
FlixFlux
Isohunt
Mininova
The Pirate Bay
TorrentSpy

Accountancy search engines

IFACnet

Medical search engines

Entrez (includes Pubmed)
GoPubMed (knowledge-based: GO - GeneOntology)
Healia
KMLE Medical Dictionary
MeshPubMed (knowledge-based: MeSH - Medical Subject Headings)
Searchmedica
WebMD

Property search engines

Home.co.uk
Rightmove
Zillow.com

Business search engines

Thomasnet (United States)
Business.com
Nexis (Lexis Nexis)

Comparison shopping search engines

Google Product Search (formerly Froogle)
Kelkoo
MSN Shopping
MySimon
NexTag
PriceRunner
Shopping.com
Shopzilla (also operates Bizrate)

Geographic search engines

Géoportail
Google Maps
MapQuest
Windows Live Maps
Yahoo! Maps

Social search engines

Google Co-op is a platform provided by Google that allows web developers to feature specialized information in web searches, refine and categorise queries, and create customized search engines
Rollyo
Wink provides web search by analyzing user contributions such as bookmarks and feedback

Search engines for kids

Yahoo! Kids
Quintura Kids

Desktop search engines

Autonomy — IDOL Enterprise Desktop Search.
Beagle — Open source desktop search tool for Linux based on Lucene
Copernic Desktop Search
Docco — based on Apache's indexing and search engine Lucene, and it requires a Java Runtime Environment.
Filehawk — Indexes and searches files' content in computers, networks and removable data storage devices
Gaviri PocketSearch — Indexes desktop, network drives and portable devices.
Google Desktop — Integrates with the main Google search engine page.
imgSeek — Desktop content-based image search
ISYS Search Software — ISYS:desktop search software.
Likasoft Archivarius 3000
Meta Tracker — Open Source Linux desktop search
Spotlight — Found in Apple Mac OS X "Tiger".
Terrier Search Engine — desktop search for Windows, Mac OS X (Tiger), Unix/Linux.
Tropes Zoom — Semantic Search Engine.
Windows Desktop Search — MSN Search Toolbar includes Windows Desktop Search which incorporates much of the desktop search technology initially promised for Windows Vista, the next version of Microsoft Windows. The search integrates into the task bar and Internet Explorer windows.
X1 Desktop Search, renamed X1 Enterprise Client

Legal

WestLaw
Lexis (Lexis Nexis)
Q uicklaw

Usenet

Google Groups (formerly Deja News)

Defunct search engines

Google Answers
Inoseek
Inktomi
Northern Light
Overture.com (formerly GoTo.com)
PubSub
Singingfish
Teoma
World Wide Web Worm.