I just blogged about using the Service Calendar as a corporate calendar. I noted that it is not available out of the box in the Outlook client. I've just experimented a bit and managed to expose the Service Calendar in my Outlook client.
To do so, you must modify the Site Map and remove the Client="Web" item from the Service Calendar entry. Below is the Site Map entry before modifying it. Be sure to save a copy of the original before you modify the Site Map. If you screw it up, you might not be able to access CRM!
<Group Id="SM" ResourceId="Area_Scheduling" IsProfile="true">
- <SubArea Id="nav_apptbook" ResourceId="Homepage_AppointmentBook" Icon="/_imgs/ico_18_servicecal.gif" Url="/sm/home_apptbook.aspx" Client="Web">
<Privilege Entity="activitypointer" Privilege="Read" />
<Privilege Entity="service" Privilege="Read" />
</SubArea>
</Group>