Dictionaries

Alcwin.org
Site listing several types of dictionaries related to the sciences.
http://www.alcwin.org

The American Heritage Dictionary of the English Language
Contains over 90,000 entries, including 70,000 audio word pronunciations.
http://www.bartleby.com/61/

ArtLex
Dictionary of visual art defines more than 3,500 art-related terms. Also includes a comprehensive collection of artwork and famous quotes.
http://www.artlex.com/

Biographical Dictionary
Read about more than 28,000 notable men and women from history. Search by names, dates, professions, achievements, and more.
http://s9.com/

DinoDictionary.com
Features profiles of over 300 known dinosaurs along with pronunciations of their names.
http://www.dinodictionary.com/

eLook Dictionary
Provides definitions, synonyms, and related words.
http://www.elook.org/dictionary/

Fact Monster
An online dictionary with definitions of more than 125,000 words and links to other related student tools.
http://dictionary.factmonster.com/

Free On-line Dictionary of Computing
A searchable dictionary of terms from computing and related fields.
http://foldoc.org/

Giraffian Children's Picture Dictionary
A collection of illustrated words and concepts, aimed at children in preschool or early primary years.
http://www.giraffian.com/pictionary/

Ice Phoenix Vocab Project
Downloadable program that looks up entire lists of vocabulary words.
http://iphoenix.sourceforge.net/

InfoVisual
Thematic visual dictionary that focuses on learning through images. Concise definitions within the fields of vegetal biology, animal biology, human anatomy, and transportation.
http://www.infovisual.info/

The Internet Picture Dictionary
Free, online multilingual picture dictionary with interactive activities for English, French, German, Spanish, Italian and ESL learners.
http://www.pdictionary.com/

Little Explorers
Picture dictionary gives definitions, pictures, and Internet links for over 2,350 entries. Includes translations for English to and from Dutch, French, Spanish, and more.
http://www.enchantedlearning.com/Dictionary.html

NetLingo Dictionary
Provides a glossary of Internet jargon and acronyms.
http://www.netlingo.com/

OneLook Dictionary Search
Type in a word and search many dictionaries at once. Also has a reverse dictionary and translations.
http://www.onelook.com/

Pidic.com
An online picture dictionary with thousands of images
http://www.pidic.com/

PSEUDOdictionary
Defines everyday words including slang, webspeak, and colloquialisms.
http://www.pseudodictionary.com/

RhymeZone
Online rhyming dictionary. Search for a word and get a list of potential words that rhyme in addition to a definition.
http://www.rhymezone.com/

The Skeptic's Dictionary
Definitions and essays on occult, paranormal, and supernatural ideas and practices from the point of view of someone who is a sceptic, that is, does not believe in these things.
http://www.skepdic.com/

Tech Terms Computer Dictionary
A searchable dictionary of computer terms with definitions explained in simple language.
http://www.techterms.com/

Terminology Collection: Online Dictionaries
Glossaries for several languages and for specialized fields from the University of Vaasa, Finland.
http://lipas.uwasa.fi/comm/termino/collect/

WebDictionary.co.uk
Online dictionary and reference website.
http://www.webdictionary.co.uk

Webopedia
Definitions of many computer-related terms, from hardware to the internet.
http://www.webopedia.com/

wordIQ
Search on several different dictionaries, an encyclopedia, and the web.
http://www.wordiq.com/

Wordsmyth
A dictionary and thesaurus in one. Also gives parts of speech and examples for more than 50,000 words.
http://www.wordsmyth.net/