Sybrina's Phrase Thesaurus  
   A creative phrase tool for creative writers of any genre including college students, people just learning English, people wanting to improve their communication skills, artistic professionals and others.
   http://www.sybrina.com

Germ  
   Searchable WordNet and Roget's Thesaurus with meaning trees.
   http://www.germ.cz/

WordNet - a Lexical Database for English  
   An on-line lexical reference system whose design is inspired by current psycholinguistic theories of human lexical memory. English nouns, verbs, adjectives and adverbs are organized into synonym sets, each representing one underlying lexical concept. Diff
   http://www.cogsci.princeton.edu/~wn

WWWebster Thesaurus  
   Merriam-Webster Thesaurus
   http://www.m-w.com/thesaurus.htm

Wordsmyth Educational Dictionary-Thesaurus  
   Integrated english dictionary and thesaurus.
   http://www.wordsmyth.net/

Bartleby.com: Reference  
   Includes "Roget's International Thesaurus of English Words and Phrases" and Houghton-Mifflin's "Roget's II: The New Thesaurus," third edition.
   http://www.bartleby.com/reference/

Roget's International Thesaurus of English Words and Phrases  
   Online publication of this popular thesaurus made available by Bartleby.com.
   http://www.bartleby.com/110/

INGRID Library Thesaurus  
   Allows direct term search with results hyperlinked to broader and narrower search terms. Available in English and Estonian.
   http://ingrid.utlib.ee/thesaurus.html

Historical Thesaurus of English  
   Contains the vocabulary of English from the earliest written records to the present, with known recorded dates of usage, taken from the Oxford English Dictionary.
   http://www2.arts.gla.ac.uk/SESLL/EngLang/thesaur/homepage.htm

Yahoo! Roget's II Thesaurus  
   Contains over 260,000 synonyms and cross-references. Features succinct word definitions and hyperlinked category index.
   http://education.yahoo.com/reference/thesaurus

Roget's Thesaurus - As distributed by Project Gutenberg  
   E-text of Roget's Thesaurus No. Two, which is derived from the version of Roget's Thesaurus published in 1911.
   http://asadz.com/thesaurus/

Phrases Thesaurus  
   A resource for writers. Enter a single word and it will return a list of phrases and sayings that are related to the word in some way. In English.
   http://www.phrasefinder.co.uk

HASSET  
   Provides direct term search followed by hierarchical and other types of browsing. Based on a UNESCO thesaurus.
   http://www.data-archive.ac.uk/search/hassetSearch.asp

Lexical Freenet  
   Search for relationships between words and concepts that might never have occurred to you before.
   http://www.lexfn.com/

Roget's Interactive Thesaurus  
   Roget's Thesaurus of English words and phrases.
   http://thesaurus.reference.com/

American Society of Indexers - Thesauri Online  
   Annotated directory.
   http://www.asindexing.org/site/thesonet.shtml

Plumb Design Visual Thesaurus  
   An exploration of sense relationships within the English language. By clicking on words, you follow a thread of meaning, creating a spatial map of linguistic associations.
   http://www.visualthesaurus.com/