I have just added a link in the Drupal Staff Web, under Departments, Reference to Tara’s list of databases which visitors and alumni do not have access to.  It includes databases which have a”limited” number of users (like one person can use it at a time or two or whatever). 

http://blogs.lib.luc.edu/reference/files/2011/10/Restricted-and-Limited-User-Databases.pdf