I’ve pointed to a number of resources on microformats in these pages. They were all written to explain how to create some particular microformat. Now there’s an article by John Allsop that not only tells you how to do it but gives a very clear explanation as to why microformats are a needed standard addition to HTML. Vitamin: Add microformats magic to your site Allsopp said,
Often they [web pages] contain very similar information – from mundane things like contact details for individuals and organizations, to reviews of films, restaurants, books, to opinions about what’s worth reading online. Yet aggregating all those contacts details to create a distributed Yellow pages-like service, or those opinions about restaurants, books, films, gadgets to create decentralized versions of IMDB reviews, or Amazon books reviews, or Zagats, is very hard, because there are no standardized formats on the web for contact details, or reviews, and many many other kinds of commonly published information. The wisdom of the web, the collective opinions and attitudes expressed there are largely inaccessible, because software isn’t smart enough to recognize it.
ADDENDUM: Another article on the same topic by John Allsop is also in the latest Digital Web Magazine. Same topic, different article. Read both.