For people with root servers running Red Hat or Suse, this might be quite useful: the linked script converts a machine running Suse or Red Hat to Debian while the system is running, and even transfers some configuration settings. However, it's still beta, so the application could also leave behind a useless pile of rubble - you probably shouldn't apply it to a fully configured system that's already in operation. It's better to use it with a still-virgin configuration.