XML and Web Services Reference Guide "We start with a discussion of Google Base, Google's attempt at a semantic search engine, which
enables you to add information in such a way that it can be searched intelligently, with queries such as "engineering job in New York, more than $40,000 a year." From there, we move on to a discussion of Microformats, or standard representations of information you put on the web every day, such as addresses, events, and reviews. Next, you need a way to easily publish that information, so we look at StructuredBlogging, a plug-in that enables you to easily add structured data to your blog. Finally, we'll look at Live Clipboard, handy little technique that enables you to move structured information such as events and contacts from one place to another with the same ease you currently have in moving a chart from your spreadsheet to your word processor."
Also, Amazon and SPARQL.