Kubuntu is the KDE-ized edition of Ubuntu Linux, the current Linux glamour distribution. Ubuntu is an excellent distribution, and I believe its popularity is due largely, in addition to technical and design excellence, to the Ubuntu philosophy. This is a lovely change of pace from the "survival of the loudest" atmosphere of some tech communities.
As nice as Kubuntu is, the default installation doesn't fit every user. This article shows how to get help, get access to more software packages, set up a firewall, and review and get rid of unnecessary services. This article covers Kubuntu 5.10, Breezy Badger.
Adding KDE to Ubuntu
Getting More Software
Setting Up a Firewall