microformats | About microformats
Designed for humans first and machines second, microformats are a set of simple, open data formats built upon existing and widely adopted standards. Instead of throwing away what works today, microformats intend to solve simpler problems first by adapting to current behaviors and usage patters

Everybody else is linking to and talking about them so I figure I might as well help with the pagerank and the spread of yet another bloody buzzword.