From the site:
Microformats are tiny bits of markup in web pages that label contacts, events, reviews, addresses, geo-locations, and other commonly published chunks of information. Microformats are often published on blogs and in feeds, but are increasingly published on other types of web pages as well such as event databases, social network profiles, reviews sites, and contact information pages. Traditional ping services only handle blog or feed updates, so we’ve set up Pingerati to handle microformat updates on any web page.
Pingerati is also a ping router (multiplexer). Pingerati receives updates of pages with microformats from numerous sources, and sends those pings to services that support microformats.