Plip and I both started on this simultaneously, luckily on different controls. We've combined our efforts and last night I uploaded the first, rather raw implementation of three server controls that emit Microformat markup: hCard, hCalendar and hReview. There is a fair way before we can mark this as a release, but it's a start; plenty of issues to keep us going in our copious spare time.
We're using CodePlex for the project, so take a look at the code if you want and add to the forums with ideas and comments.