VZ Members is my second fieldtype for Brandon Kelly’s FieldFrame extension. I needed a way to select any number of site members to associate with an entry. In my case I am doing this to allow entry creators to set permissions on an entry-by-entry basis. You could also use it to link to the profiles of people mentioned in an article, or inside a Matrix field to create a list of events, each with a date, title, and the personnel who will be in attendance.