Ping the Semantic Web
RDF publishing service
PingTheSemanticWeb or PTSW as it has affectionately come to be called is a repository for RDF resources. Once subscribed, the service is notified whenever a new RDF resource is created or updated. External users can also import the list of recently created/updated RDF documents, and various APIs are available to access the service. About 1 million resources are presently being tracked by PTSW, and it has become an authoritative source for the status and statistics of RDF, namespaces and the semantic Web.