Microformats
Microformats.org is a community for microformats advocacy, education, and technical information. 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 (e.g., XHTML, blogging).

Visit the Microformats wiki
Read Microformats’s blog