I recently installed the Operator extension in my browser.
Operator leverages microformats and other semantic data that are already available on many web pages to provide new ways to interact with web services. [Operator :: Firefox Add-ons]
Interesting to see it in action on the JISC National eBooks Observatory page above. It recognizes address and contact data. Clicking on address displays an address, and offers to show it on Google and Yahoo maps.
I could also have used LinkedIn as an example where some structured data is also exposed using microformats. LinkedIn is one of the examples used by Yahoo in its much discussed announcement the other day about its support for various structured formats.
While there has been remarkable progress made toward understanding the semantics of web content, the benefits of a data web have not reached the mainstream consumer. Without a killer semantic web app for consumers, site owners have been reluctant to support standards like RDF, or even microformats. We believe that app can be web search.
By supporting semantic web standards, Yahoo! Search and site owners can bring a far richer and more useful search experience to consumers. For example, by marking up its profile pages with microformats, LinkedIn can allow Yahoo! Search and others to understand the semantic content and the relationships of the many components of its site. With a richer understanding of LinkedIn's structured data included in our index, we will be able to present users with more compelling and useful search results for their site. The benefit to LinkedIn is, of course, increased traffic quality and quantity from sites like Yahoo! Search that utilize its structured data. [Yahoo! Search Blog: The Yahoo! Search Open Ecosystem]
The entry goes on to describe the support that Yahoo will be providing for microformats, metadata vocabularies and opensearch.
Google released its Social Graph API a little while ago.