The Department of Computer Science uses an Oracle calendar system, which can be accessed from either a native client (i.e. a Mac, Windows or Linux program that you install on the computer from which you want to use the calendar) or by using a web client. The calendar is provided as a NFIT service for the whole Faculty of Science, so you can read more about it on http://calendar.au.dk/
Using the calendar you can book your colleagues for a meeting and even reserve a room for the meeting and book the department car.
The rooms have weblinks that allow you to see the public details for the arrangements in them without logging in, i.e. http://calendar.au.dk/cal.php?res=DI-5510.103+%28Store+Aud.+%C3%85bogade+15%29&view=month is a link to the calendar for Store Auditorium.
The current policy is to provide all employees with a calendar account and all students who apply for one. Send an email to helpdesk@nfit.au.dk if you want a calendar account and don't already have one.