It is simple to share your calendar with other users on the same Exchange server. To do so, click on Calendar View and in the left-hand pane click on the blue underlined 'Share My Calendar...'
Slightly unexpectedly, a new email will appear. Type the name or the person you wish to share with into the To: field and click 'Send'. You will be asked to confirm that you want to share your calendar with this person. Click 'OK'
The person you have shared with with receive an email informing them. To see your calendar they simply have to click on the 'Open this Calendar' button in the top left corner. Once this has been done they will be able to view your calendar along-side their own whenever they open Outlook.
This series of actions only provides the lowest level of sharing. The person with whom you have shared will simply be able to see your appointments. To change their level of access so that they can create or change appointments go to Calendar view and right click on 'Calendar' underneath 'My Calendars'. Select 'Properties...' and a new window will open. Click on the 'Permissions' tab and you can choose your sharer and customise their access.
Click OK and the new settings will be saved. Take care to set access limits at their most conservative level to avoid risking your appointments being accidentally moved or deleted by other users.