MultiSchedule 

Want to setup your company's calendar scheduling software on network? Want to share appointment schedules among staff? Want multiple users to be able to access the calendars in real time simultaneously? Want it to be able to synchronize with Outlook?
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iCal 

iCal is a web calendar server. Anyone with a web browsers can access the calendars on their local Intranet or Internet. Any number of calendars can be created and accessed by any number of users. Security controls who can make calendar entries.
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