Collaborative Applications with their participants
Command and Control or more generally distributed (tactical) real-time decision support -- decision makers and gatherers of information
Forums and Chattering on the Web -- the world!
Education -- teachers and students (and administrators)
(Tele)medicine -- Doctors (primary and specialist referrals), Nurses, Patients and administrators
Business Enterprise (strategic) Support as in Lotus Notes -- Employees of Business including especially managers
Multidisciplinary Applications including Collaborative design -- teams of multi organization engineers
Computational Steering -- one or more computational scientist and visualization device