At Yahoo! Search we use RDF to crawl for semantic data and power our Rich Results. Check out searches for "thai chili" and "paul tarjan facebook".
If you want to see all the semantic data we pull out of pages, install the "Structured Data Display" SearchMonkey plugin and under every result you will see an inforbar full of the RDF serialized as RDFa. (I can't post links since I'm new here).
