CRM provides functionality for the Users to log into the screen of their choice. This setting can be changed from the User preference area of CRM. However, the same is still not achieved in Self Service Support Site for the Self Service users. Whenever Self Service users login to the support site they may see the screen with the details of recent Customer Care issues and Opportunities as shown in the below screenshot.
If you will go through the custom pages for Support Site, you can find that this is the page called Caselist.asp. Suppose you want the Self Service user to login to the different area of Support site you can let this page redirect to the one of your choice instead of Caselist.asp and accordingly you may need to change the other pages to handle the change of redirection.