The Linked Open Vocabularies site collects metadata and statistics about the RDFS and OWL vocbularies used in the Linked Open Data cloud. It looks like an interesting and useful resource.

“Welcome to LOV, your entry point to the growing ecosystem of linked open vocabularies (RDFS or OWL ontologies) used in the Linked Data Cloud. Here you will find vocabularies listed and individually described by metadata, classified by vocabulary spaces, interlinked using the dedicated vocabulary VOAF. You will enjoy querying the LOV dataset either at vocabulary level or at element level, exploring the vocabulary content using full-text faceted search, and finding metrics about the use of vocabularies in the Semantic Web. Not finding your favourite one? Suggest a new vocabulary to add to LOV!”