A long time ago (almost 1000 posts ago!), I talked about an alternative to FOAF I had dreamed up, called PROFILE. I'm still not a big fan of FOAF's RDF-ishness, but I love open-ness more, and FOAF is the only moderately widespread profile interchange format today (my FOAF is here, thanks to the Drupal module James wrote).
I expressed it really badly back then, but what I wanted PROFILE to be was an XHTML-valid format so that it would easily display within web pages using nothing but CSS for styling, but still have enough semantic meaning to be machine-parsable.
So the next target is calendaring information. Tantek calls it hCalendar, inspired by some work at foocamp04 on HTMLForCalendars.
I recently wrote up some thoughts on syndicating events using iCal in Drupal. That is, embed/attach iCal to RSS feeds. This will likely still happen (lots of people can easily consume iCal compatible information today). But for web-to-web representation, especially in feed readers, an XHTML compatible format would provide easy display today.
Hat tip to kellan for the Tantek related links.