I added XFN (XHTML Friends Network)
to my blogrolls. XFN is some kind of poor man FOAF. You can define your
relationship within the a element in a simple and standardscompatible
way. Just add a rel attribute to your link and add your relation to
that person. I extended the ābloglinksā table with an additional field
ārelā for easy maintenance of this. See their profile page for the possible values.
There's also a aggregator for this, which shows these relations. It's called rubhub. It has currently some spam issues and my site isn't indexed yet
What I like about XFN is it's simplicity in contrast to FOAF. FOAF
on the other is much more powerfull, but with a decent implementation
in a blog, those two are certainly combinable somehow.