The guys at Talis have done a good job of evengelising linked data as a concept, the basic tools and their platform. If you are new to the space then the presentation by Rob Styles (44 mins) (from the Linked Data and Libraries event on 21st July 2010) is worth watching. In particular he does a good job of explaining what RDF is (a graph data model) – as against the different ways in which you can write it down e.g. Turtle, RDFa and RDF/XML. His whiz through SPARQL gives a useful intorduction to how RDF data can be queried.