One thing I often hammer on about is the essential re-usability of open content. Here's a good example: AskWiki, a kind of semi-intelligent front-end to Wikipedia that lets you frame questions it attempts to answer autonomously using that body of information:
AskWiki, developed in partnership between AskMeNow and the Wikimedia Foundation, is a preliminary integration of a semantic search engine that seeks to provide specific answers to questions using information from Wikipedia articles.
What's particularly cool is that is also applies classic Darwinian evolution through collaborative refinements:
Users can improve the accuracy of the AskWiki engine via the categorization feedback mechanism. Users can categorize each AskWiki Answer as an article deemed either Correct, Incorrect or Uncertain. This user feedback is processed by AskWiki to improve the search capabilities and accuracy of the AskWiki engine.
Members of the AskWiki Community are encouraged to expand upon correct answer articles and correct the incorrect or uncertain ones, re-categorizing the articles as they are updated. These efforts are tied directly into the AskWiki engine as well.
Although very simple at the moment, this has great potential. Wikipedia is rather passive, waiting for you to find stuff; AskWiki, by contrasts, tries hard to "understand" what you want, and give it to you. Now extrapolate the "understand" bit, and you get something very interesting.... (Via Language Log.)