Cambridge Dictionaries Online

Merriam-Webster Collegiate Dictionary and Thesaurus Online

Newbury House Online Dictionary

Oxford English Dictionary

Wordsmyth Educational Dictionary-Thesaurus

YourDictionary.com--Multiple Language and Specialty Dictionaries

Dictionary.com

Thesaurus.com

Language Dictionaries (YourDictionary.com)

Travlang's Translating Dictionaries

Endangered Language Repository (YourDictionary.com)

Internet Dictionary Project

Specialty Dictionaries (YourDictionary.com)

Multiple Language and Specialty Dictionaries (Dictionary.com)

Academic Press Dictionary of Science and Technology

FOLDOC (Free On-Line Dictionary of Computing)

Online Medical Dictionary (graylab)

Medterms.com

Life Science Dictionary (U Texas)

Webopedia Dictionary of Computing and Internet

ArtLex Art Dictionary

Biographical Dictionary

Duhaime's Law Dictionary

Law.com Dictionary

Dictionary of Phrase and Fable

RhymeZone.com Dictionaries of Rhymes, Quotes, etc.

Dictionary of Units, Measures and Conversions