Semantic Web Possibilities

Today I listened to a great interview of Elias Torres by Phil Windley; the podcast is linked from here:

http://www.windley.com/archives/2006/08/elias_torres_on_sparql.shtml

Elias discusses the Semantic Web layer cake of tools, and focuses on SPARQL, the RDF query language.  It's a technical topic, but the conversation is very accessible to non-programmers.  My head's been churning all day with possibilities that seem interesting.  One idea: cross-site, heterogeneous-data collaborative filtering.  For example, crossing voting patterns on social bookmarking sites with Amazon's "Statistically Improbable Phrases" (sorry, what marketing genius wrote that label for such a useful feature?) gets you, "If you liked this article, you might also like these books..."