Ontology

•  OpenCalais - RDF-based annotation of natural language, maybe the ontology is reusable for you

RDF libraries

•  RDF2Go is a convenient abstraction layer that can use Sesame, Jena, and others as backends
•  Sesame, has a SPARQL endpoint
•  Jena, has a SPARQL endpoint
•  JRDF looks like an academic prototype that is better for some tasks, but not yet for "just getting your work done"
• SWI Prolog also supports RDF ( semweb package,  RDF parser); doesn't have a SPARQL endpoint itself, but there are third-party ones:
  •  ClioPatria, a complete RDF store on top of SWI Prolog
    •  Publication about an actual semantic web application done with SWI Prolog
  •  Another SPARQL endpoint for SWI Prolog, maybe usable
  •  Tutorial on RDF with Prolog

Querying

•  SPARQL

Scaling to the Web

•  Recent publications about Annotea -- not too impressive, but I haven't looked into them.
•  dbpedia