This page lets you execute SPARQL queries against the Semantic Web Search cache of crawled files. You can select from several example queries or enter your own. If you want to use your own SPARQL client here's the necessary information:
NOTE: this uses a betaversion of our SPARQL support package, so please let me know if something doesn't work that should. Also, I've set the query governor, so complex queries might fail. Using LIMIT on complex queries might enable them to succeed where they would otherwise fail.