Maintaining a resource in a public folder is a variation on the direct creation theme.
Users who want to schedule the resource make appointments directly in the public folder.
For Exchange 5.5, the Auto Accept Utilitiesby Robert Strong handle recurring meeting requests, allow you to restrict access to a particular resource through a distribution list and perform optional diagnostic logging to a folder in the resource's mailbox.
Custom attributes on the resource mailbox control the optional features. If you are booking the resource with a script, you should not open the Calendar folder directly.
In the Microsoft Exchange Administrator program, you can use the Delivery Restrictions tab on the Properties dialog for the conference room’s mailbox to allow only certain people to send messages to the conference room.