Bernie just put together this beauty to load small RDF/XML files into Virtuoso’s metadata store (We are using testing the open source version).

DB.DBA.RDF_LOAD_RDFXML(http_get ('URI to the RDF/XML file'),'','Name of the graph in the store');

We have tested loading a 5 Million triple RDF/XML and results are pretty nice (It took around 6 minutes to load into a dual Pentium 4 extreme edition at 3GHz with 4GB of RAM on a slow 7500rpm ext3fs). When pushing to larger files, the stream version of this is a must to reduce memory consumption.