Google is one of several search engines that index and support microformats.
See google-rich-snippets-examples for documentation of Google's microformats examples (along with a few corrections/improvements). See Jeni's blog post on What’s wrong with Google's RDFa Support for a description of the numerous problems in the *RDFa* documentation/implementation of "rich snippets". (To Do extract these instances of real world problems, analyze for causes, and note principles and techniques for avoiding them in the future.)
Through additional user interfaces:
Google provides search APIs like:
- Google Social Graph API supports XFN - The XHTML Friends Network (launched 2008 February). See "Google Social Graph API How are your sites connected?".