Getty Thesaurus of Geographic Names Search the name of any place in the world and find out where it is on Earth. Includes ancient place names and variants of current names.
http://www.getty.edu/research/conducting_research/vocabularies/tgn/
Plumb Design Visual Thesaurus Use this tool to explore, study, and analyze the structure of language and the interrelationships between words and meanings.
http://thesaurus.plumbdesign.com/
Visual Thesaurus Online Edition Helps you literally picture words and their synonyms by displaying their relationship graphically.
http://www.visualthesaurus.com/online/index.html
