If you are using an Exchange server...
Pick someone willing to lose their calendar for personal use. Have that person share (right-click, properties, permissions tab) with the other persons. Everyone puts their *business* appointments on it. Then everyone's on one calendar.
The calendar can NOT be anything other than the default Outlook calendar. If the person who gave up their calendar wants their own personal one, they'll have to create a personal folder (tools-services) and put one in that.
Better yet, if your mail administrator will do it, have them set up a new mail account or public folder with a departmental calendar in it. Give rights to your department members only.
If you are not on an exchange server, you're basically SOL and might want to consider just creating a calendar in Word, and sharing that file on a shared drive. Excel would be even better, because more than one person can access an Excel file at one time, before placing file on shared drive, just hit Tools-Share... I have seen some Excel calendars online. Try the Appointment Calendar maker at
http://j-walk.com/ss/excel/files/general.htm