Two ideas: First, meeting requests. The person scheduling creates a meeting request in Outlook, they can see when people are busy, tentatively scheduled for something else or out of the office on the second tab of the meeting request. When they send it, everybody can accept or reject the meeting. They can also automatically accept: Tools...Options, Calendar Options, Resource Scheduling.
Second idea, set everybody up as delegates for each other (Tools...Options, Delegates). Then they can go to the File menu and Open Other User's Folder to open each other's calendars and set appointments. May also have to right-click on each person's calendar, choose Properties, then Permissions I think and add every user as being allowed to see and edit the calendar. Kind of long process. I prefer the meetings. Hope that gets you started!