Em Space use Case Tracker as our support system. Casetracker Services is a contributed module uses Services to allow Drupal sites to connect/integrate with a central Case Tracker support site.
-- Look at Case Tracker features and usage.
-- Go through Case Tracker Services, it's features and configuration options.
-- See how intermediate parties (like Design companies) can monitor client sites.
-- Use one service as a quick example of how to implement custom services.
-- Audience to understand the scope of Casetracker Services and get a little idea of what "Services" are in general.
Simon Hobbs maintains Casetracker Services and uses it in conjunction with Case Tracker as a support site for Em Space.