I used GW as an example because that is what I am most familiar.
Features:
* Every user will keep their personal calendar up to date
* There is an interface to schedule meetings that then appear on everyone's calendars
* A central user list that is owned by this application
* A central schedule that is owned by this application
add
* Notification feature to remind user of meeting
* Facility list owned by application to prevent double booking of a room
* Find meeting time. I want to meet with Drew, Wade and Norm. Find a time that all of us are available.
* Allow user to accept or reject the meeting. Not "scheduled" until user accepts meeting.
* Cancel meeting or change meeting date or time
These were the basic features that groupwise offered.