wp-RDFa allows you to create machine readable content from your wordpress blog. This concept of a semantic web computers to perform more of the tedious work involved in finding, sharing, and combining information on the web. You can find out more here.
The Friend of a Friend (FOAF) project is used to create a Web of machine readable pages describing people, the links between them and the things they create and do. Here you can tweak the output of your FOAF file, acknowledging only certain users on your blog and tagging the work they do. By default its assumed that you only know higher level users on your blog. This information acn then be cross reference with other FOAF data.
Show the relationships between you and your blog users (Acknowledge in FOAF that you know them). This can be defined on a per WordPress roll basis.
wp-RDFa uses the Dublin Core vocabularly to mark up blog posts and accredit the work to the author and the url of the post.