One of the common weaknesses of existing social network services is the lack of easy flexible ways to differentiate types or depth of friendship.  Orkut, for example, allows one to group friends but also requires one to name each group.  While this requirement seems trivial and makes sense logically, it deters users from using the feature in practice.

Friendship Circle is a way to express types and depths of friendship with minimal effort.  A Friendship Circle is basically a nested rings of people (represented by icons with miniture photo and name) around a person.  To use the Friendship Circle, the user drag and drops icons from a palette of friends to the circle.  Note that this can be done using DHTML+CSS.

Distance away from the center represent depth of friendship.  So the innermost ring is populated by family members, relatives, and best friends.  The outermost ring is populated by people whom you don't really care about (i.e. connection-addicts).

Angle of placement on a ring is used to express types of friendship.  To help the user, the rings are divided into four lightly colored quadrants: red, blue, green, and yellow.  Red and blue quadrants will most likely be used to hold people with personal and business relationships.

Update:

I drew up a mockup of Friendship Circle for those having trouble visualizing from my description.