Adaptive context access
The first real module of adaptive context (ac) is the access module. It allows users to select access over users, groups and roles. Depending on what the admin allows of course. The concept of audience and access comes originally form organic group that allows public or private access, this module is a full and standalone version of that idea.
The module has also a big experiment with javascript/jquery to make the selection easer, it depends also on jqselect.module.