Semantic Theory Links
Roget's Thesaurus, Categorization
List of Words' category system is (loosely) based on the one used in Roget's Thesaurus from 1852 (all links open in new window).
Wikipedia article about Roget's Thesaurus
Tesoro español o Diccionario de ideas afines (1899)
Semantic Networks
Take a look under the hood! These sites have introductory information on semantic networks, examples and downloadable material.
Wikipedia article about semantic networks
Semantics and Artificial Intelligence
Wikipedia article about knowledge representation