Dictionaries

A.Word.A.Day
American Heritage Dic of the Eng Lang (4th ed)
Business Dictionary
Cambridge Dictionaries Online
Collins Cobuild Dictionary
Collins Dictionary
Collins Language
Definitions of Thesaurus
Dictionary
Dictionary.com
Dictionary - MSN Encarta
Dictionary and Thesaurus
Dictionary Search Page
Dictionary Software
English Dictionary and Reference
English Glossary of Grammar Terms
English Synonym Dictionary
Free Dictionary, The
Free Dictionary by Farlex
Google Definition Search
Infoplease.com (Dictionary)
Lexical FreeNet
Look Way Up
Macmillan Dictionary and Thesaurus
Merriam-Webster Online
Memidex - Outstanding Word Explicator 
Mnemonic Dictionary
ODLIS- Library and Information Science
OneLook Dictionary (Thesaurus)
OneLook Dictionary Search
OneLook Reverse Dictionary
Online Dictionary and Much More
Online Etymology Dictionary
Oxford Advanced Learner's Dictionary
Oxford Dictionaries Online
Oxford English Dictionary (OED)
Plain Text English Dictionary
Public Reference Tools - The ARTFL Project
Rhyming Dictionary and Thesaurus
Roget's Thesaurus (1911)
Roget's Thesaurus (1991).html
Roget's Thesaurus (Notre Dame)
Roget's Thesaurus [city.ac.uk]
Roget's Thesaurus Search Form
Synonym
Synonym Dictionary (Vancouver Webpages)
Synonym Finder and Thesaurus
Synonyms and More
Synonyms and Related Words Dictionary
Synonyms Thesaurus
Thesaurus Web Guide
Thesaurus, Phrases, and Quotations
Thesaurus.com
Urban Dictionary, April 5- office quarterback
Urban Dictionary, August 20- Folicular Homicide
Visual Thesaurus
Webopedia
WordNet
Wordnik- All the Words.
Wordsmyth
WordWeb 6.3
Your Dictionary