DBpedia is a crowd-sourced community effort to extract structured information from Wikipedia and to make this information available on the Web.
RelFinder - Interactive Relationship Discovery in RDF Datasets
Now that we’ve published nearly 10,000 of our tags as Linked Open Data , you’re probably wondering what kind of cool applications you can build with this data.
Virtuoso SPARQL Query Form
Generating RDF from data.gov - Data-gov Wiki From Data-gov Wiki
The Freebase Blog » Blog Archive » Introducing the Freebase RDF service