Restrict Admin Privileges to Organizational Units

Google Apps super admins now have the ability to designate users as admins for specific organizational units. Users in a domain can be arranged in organizational units to better control the services and features they have access to.

For more information:
http://support.google.com/a/bin/answer.py?hl=en&answer=182433
http://support.google.com/a/bin/answer.py?hl=en&answer=172176