For example:

If you tag your contact information (using the hCard format), then someone clicking on it can instantly add you to their address book, or find you in Google Maps.

If you tag an event (using hCalendar), then someone clicking on (such as from eventful.com) it could automatically add it into their Google Calendar, or iCal.

Who’s using them, and how?

Microformats are being used more and more by sites like Eventful.com, and is already being supported by Yahoo and Microsoft, in Google Maps, and it’s built-in to Firefox 3.

The takeaway for MailChimp customers is that microformats have a lot of potential, so to help you keep your email marketing ahead of the curve, we automatically embed microformat code into your email campaign footers. You can expect even more microformat support in future MailChimp releases.