NASA Thesaurus  
   National Aeronautics and Space Administration Thesaurus. Extensive coverage of scientific terms.
   http://www.sti.nasa.gov/nasa-thesaurus.html

CAS General Subject Vocabulary Helper  
   Extensive listings for chemistry. Produced by Chemical Abstracts Service, a division of the American Chemical Society.
   http://www.cas.org/vocabulary/index.html

Maths Thesaurus  
   Definitions of common mathematical terms, along with broader, narrower, and related concepts.
   http://thesaurus.maths.org/

Babynames Thesaurus  
   You can search for a name from its meanings. The site has more than 10,000 names with meanings.
   http://www.yourbabysname.com/thesaurus.htm

Art and Architecture Thesaurus  
   Getty's terms, as used in several AAT indexes.
   http://www.getty.edu/research/tools/vocabulary/aat/

Eurodic Autom  
   European Union terminology. Available on most European Union languages.
   http://europa.eu.int/eurodicautom/login.jsp

Getty Thesaurus of Geographic Names  
   Structured vocabulary of place names.
   http://www.getty.edu/research/tools/vocabulary/tgn/index.html

Library of Congress Thesauri  
   Links to multiple LOC thesauri, including GLIN, the Global Legal Information Network.
   http://www.loc.gov/lexico/servlet/lexico

Library of Congress Classification Schedules  
   A comprehensive list of LOC Classification schedules.
   http://www.loc.gov/catdir/cpso/lcco/lcco.html

Alcohol and Other Drug Thesaurus - AOD  
   National Institutes of Health thesaurus. Provides resource for medical, social, and demographic terms related to alcohol and drug use.
   http://etoh.niaaa.nih.gov/AODVol1/Aodthome.htm

ASIS Thesaurus of Information Science  
   Hierarchical and alphabetical interface to library-related terms.
   http://www.asis.org/Publications/Thesaurus/isframe.htm

Concept Space: the visual search tool for business concepts  
   A British business education thesaurus with an intriguing navigational component from the London Business School.
   http://conceptspace.london.edu/

The Astronomy Thesaurus  
   Astronomical terms. Searches may be performed in English, French, German, Italian, and Spanish.
   http://www.mso.anu.edu.au/library/thesaurus/

Thesaurus of Musical Instruments  
   Over a thousand instruments, with relational links based on the Library of Congress Subject Headings.
   http://alteriseculo.com/instruments/