The Network Manager is a project I wrote that enables us to get a high level view of whats going on with our sites. It gives you the ability to monitor any site that sits on the same server (regardless of if it's in the same multi-site configuration). It also allows you to view across versions of Drupal! Right now the manager has to be installed in Drupal 6 but there is a small connector module for connecting 5 and 7 sites into the display. You'll probably just have to play with it to fully understand why it's so darn useful but check out the screencasts on the side for more details.
Check it out at http://drupal.org/project/network_manager