Once Cups is installed (on Ubuntu 7.08 it is preinstalled) it can be accessed in the browser via
http://localhost:631/
It is important to configure the printers there, as the Gnome interface seem to work not like expected, at least for me. On the website Classes can be ignored, just add the correct printer and publish it.
On a system in the network the printer has to be configured on the system it self in the same way it was done on the printserver. The device is InternetPrintingProtocol (ipp), the device URI is
ipp://printserverip:631/printers/printername.
http://printserverip:631/printers/printername