I agree with other responders: embedding mark-up in the page using RDFa is a good approach and FOAF is the obvious place to start in terms of tags.
When I was marking up our company About page with RDFa, I also used:
GoodRelations http://purl.org/goodrelations/v1#
VCard http://www.w3.org/2006/vcard/ns#
Yahoo Commerce http://search.yahoo.com/searchmonkey/commerce/
Semantic Crunchbase: http://cb.semsol.org/ns#
You can have a look at the resulting RDF here http://www.w3.org/2007/08/pyRdfa/extract?uri=http://www.swirrl.com/about
I made up my own term to link to our twitter accounts, but I've been meaning to go back and use foaf:holdsAccount for that instead.
For blogs, it would also be a good idea to mark up each post with title and author metadata, eg using Dublin Core http://dublincore.org/documents/dcmi-terms/
There is a Wordpress plug-in http://wordpress.org/extend/plugins/wp-rdfa/ that does some of this, but I haven't used it myself. And I read that RDFa support built into Drupal is coming with version 7, though not released yet.