Sites already using microformats, includs Google, Yahoo!, Facebook, Twitter, Flickr, and LinkedIn. But these are just some of the more well-known names..
...How pervasive microformats are. For example, according to Yahoo! SearchMonkey, there are 1,450,000,000 web pages that publish hCard and 36,200,000 pages marked up with hCalendar.
Few good links to get set go: