OfficeCalendar 

Share Microsoft Outlook calendar, contact, and task information with this affordable Exchange alternative. Makes Outlook calendar sharing and Outlook group calendar scheduling easy. Works with Microsoft Outlook 2000, XP, and 2003. Free trial.
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Exchange GroupCalendar 

3 clicks, that's all you need for Exchange 2000 or 2003. Exchange GroupCalendar enables anyone who can count to three to install and manage an unlimited number of company shared public calendars.
exchange team calendar groupware free/busy public

GroupCalendar 

MS Outlook calendar sharing application based on a database in a lan. Either with or without Exchange Server you can now get a overview of all appointments of all co-workers without the use of anexternal program. Just stay in Outlook.
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