The organization where I work uses a Flash Calendar to show holidays, special day activities and other public calendar. The Flash Calendar loads its events from a XML file which, in our case, is keeped really up to date. So I was willing to view those events on my Google Calendar screen, to better plan my meatings and so on.
After that, I had written a small wrapper to parse the XML and echo iCal output. It still not fully compatible with Flash Calendar XML, but for the uses of my organization is enougth.