A good general introduction to microformats; don't let the title prevent you from looking. Microformats are "a set of open data formats used to mark up XHTML content to provide a bit of semantic meaning." Think of them as though they were XML tags embedded directly into a web page, instead of in a separate XML file. The idea is that this mark-up, usually very specific to a bit of information, can be mixed and matched with other bits of information. "Microformats already have a very specific task in mind when created and build upon prior work. This helps to avoid the extremely large and complicated specs that have become associated with XML languages."