In spite of previous disavowals of having social networking aspirations, identity link aggregator ClaimID has now added the ability to add other ClaimID members to your profile as contacts.
Interestingly, they restrict you to adding friends who have OpenIDs (since every ClaimID profile URL is an OpenID) and use the XFN microformat to define your relationship.
This is a significant decision because, presumably, every OpenID has an owner. As such, adding one of these “verified” OpenID URLs as a contact to your verified OpenID URL could represent a higher trust level — a stronger “claim” as the lingo goes — than simply using the XFN rel-me attribute to create a “weak” relationship claim. Or so goes the theory.
Meanwhile, I’ve recently been reordering my Flickr screenshot collections and have created a set devoted to adding friends interfaces. If you have examples of similar interfaces, leave me a link to the source and I’ll get them added!
Factory Joe 
Check out the facebook interface for adding friends, particularly the “how do you know this person?” screen after you friend request has been confirmed byt the other party.