What is 'Swoogle'?
Swoogle is a crawler-based indexing and retrieval system for the Semantic Web. That is, it indexes RDF and OWL documents, rather than plain HTML documents. Swoogle extracts metadata for each discovered document, and computes relations (including similarities) between documents. One of the interesting properties computed is called ontology rank, a measure of the importance of a Semantic Web document.
Swoogle is a research project of the ebiquity research group in the Computer Science and Electrical Engineering Department of the University of Maryland, Baltimore County. Partial support for Swoogle was generously provided by DARPA and the National Science Foundation.
Documentation about Swoogle can be found here, or to use the search engine itself, go here.