Updating local copies of databases and ontologies

DBpedia receives an update stream [PDF] from Wikipedia, using OAI-PMH, and incorporates changes almost immediately into a "Live Extraction" instance of Dbpedia.
There is work progressing on an XMPP update stream from Wikipedia.
BBC Music parses a live update stream from MusicBrainz.
MRS fetches bio databases and updates local copies.
James Malone/EBI's ontology-mapping tool [PDF] fetches ontologies and flags updates or conflicts.