Meeting Scheduler

As a PM the task I dread most is scheduling meetings. Just looking at everybody's schedule and finding time to do it is easy. Outlook already gives us that information. The difficult part is when there is no common free time on anybody's schedule. Then the scheduler needs to be smart about a number of things:

 * From amongst the invitees, whose time is not as important (that person can be double booked and asked to ditch his/her previous appointment).

 * From amongst the invitees whose presence is "reqd" but it is ok if they dont turn up or send in a proxy

 * From amongst the invitees whose presence is "reqd" but I dont want them to attend

 * For a really must-have invitee, is it possible to broker a good time?