KBS/Ontology Projects and Groups - Hundreds of annotated, alphabetically sorted links to ongoing work by members of the Knowledge Systems Research Group, part of the Artificial Intelligence Lab at the University of Texas at Austin. Buffalo Ontology Site - Comprehensive collection of links maintained by Barry Smith, on the philosophy faculty at State University of New York at Buffalo. European Centre for Ontological Research (ECOR) - ECOR represents a new approach in applying ontology to a variety of problems in information science and related areas, by coordinating institutions, organisations and companies working in the field. OWL Web Ontology Language Reference - Detailed description of the OWL W3C specification. Ontology is Overrated: Categories, Links, and Tags - Clay Shirky explores online categorization, contrasting ontologies with folksonomies. Ontolog - Ontolog is an open, international, virtual community devoted to advancing the field of ontological engineering and semantic technologies, and advocating their adoption into mainstream applications and international standards. Guided Tour of Ontology - Very large site comprising six papers by mathematician John F. Sowa of Harvard and MIT, each with summary introductory paragraph followed by numbered topic headings hyperlinked to detailed articles. Exhaustive summary bibliography. Ontology Online - Semantic web experiment and ontology mashup maintained by David Decraene.