Oxford English Dictionary The definitive English dictionary, containing etymologies and historical usage. (UMaine ID required)
WWWebster Dictionary (Merriam Webster). Includes definitions, pronunciations, spelling, and a thesaurus.
OneLook Dictionaries, The Faster Finder Links to more than 200 general and specialized language and subject dictionaries.
RhymeZone Rhyming Dictionary and Thesaurus Search for perfect rhymes, match ending sounds, get definitions or related words, check spelling, or find homophones, semantic siblings, or synonyms.
Roget's Thesaurus (1911 edition). A classic dictionary of synonyms and antonyms.
yourDictionary.com. Links to collections of English and other-language dictionaries and thesauri.