UfXtract is an open source .Net microformats parser.
It supports a number of microformats hCard 1.0, hCalendar 1.0, hReview 0.4 (in progress), hResume, hAtom 0.1, XFN - The XHTML Friends Network, rel="tag", Geo, adr, rel="nofollow", rel="license", rel-directory, rel="home", rel="enclosure", rel-payment and Vote Links. It also supports a handful of POSH patterns hCard-XFN, rel-me, rel-next/previous, test-suite and test-fixture. The direct support of rel-me and rel-next/previous was added to help people build social graph spiders.
The libaray can typically parse a page between 10-50ms. It ws build using test suite to help make sure it conforms as closely as possible to the microformats specs.
You can also easily create new microformats and POSH definitions using some simple .Net objects.