This document shows how allow others within your Exchange organization to access your mailbox folders, including your calendar. This particular documentation shows how to do this using Outlook 2011.
Open Outlook 2011 and click on Accounts... under the Tools drop-down menu.
Click on the + button, located on under the Delegates who can act on my behalf: box.
In the Find textbox, type the name of the person you are looking for and then click Find.
Click on the name you were searching for and then click OK.
Choose the permissions you would like to give to the person you are allowing access to. For example, if you would like a person to see your e-mail messages, and send messages on your behalf, change the Inbox drop-down menu to Editor (Can Read, Create, Modify Items). After you have chosen the permission settings click OK.