I used to say that I didn't think the W3C's Semantic Web would offer any practical applications in my lifetime, and indeed its development and progress has been painfully slow for it is a monumental undertaking. However the accelerated development of RDFa (Resource Description Framework) has seen one practical implementation that will be of special interest to Web Developers:
http://rdfa.info/ - RDFa - Linked Data in HTML
"RDFa is an extension to HTML5 that helps you markup things like People, Places, Events, Recipes and Reviews. Search Engines and Web Services use this markup to generate better search listings and give you better visibility on the Web, so that people can find your website more easily."
And the W3C has recently provided a "baby step" facility ..........
http://www.w3.org/TR/rdfa-lite/ - RDFa Lite 1.1 (W3C Recommendation 07 June 2012)
.......... to help Web Developers begin using RDFa/HTML.
Check out the above Documents for detailed information.