Knowledge Organisation Systems
Metadata Registries
Terminology Registries
BioPortal by National Center for Biomedical Ontology http://bioportal.bioontology.org/
The United Nation’s Food and Agriculture Organization (FAO) Registry http://aims.fao.org/website/KOS-Registry/sub
NERC Vocabulary Server by the National Environment Research Council http://bioportal.bioontology.org/
Open Metadata Registry http://metadataregistry.org/
OCLC's Terminology Services Pilot http://tspilot.oclc.org/resources/
The Library of Congress Authorities and Vocabularies service http://id.loc.gov/
The CENDI Science Terminology Locator http://www.cendi.gov/projects/termlocator.html
Taxonomy Warehouse by Factiva http://www.taxonomywarehouse.com/
TaxoBank by Access Innovations http://www.taxobank.org/