As most of us standards based web desingers will tell you the semantic web is coming, slowly but surely.
Microformats started all this giving meaning to blocks of divs and the like; so that chunk of HTML that is the companies web address / contact details are structured and tagged in a certain way. This makes it easier for search engines and the like to find the relative data on your website and is very very useful!
When it comes to testing to make sure your hCard etc works take a look at left logic for a great little tool!
Dont't forget to head over to microformats to read up on the does, dont's and how to's..