You want to be able to book a meeting or event with many people who are in many locations.
The obvious answer is a Microsoft Exchange based meeting system - everyone's calander is already on the system, so all you have to di is pick a slot. Unfortunately, this is not always available. It's possible to create a web page (extranet) so that each person can login and allocate time that they are free. When all recipients have selected a number of times that they are free, the meeting can be booked based upon the optimum attendance.
- the interface can be really simple as it is web based.
- It invokes some commitment from the attendees as they have allocated the time that they are free.
- You don't need a team of people to call each person and find their availability.