Quick note:- I use KDE nearly all the time. But sometimes I have occasion for a minimal desktop (e.g. when I plan to use just one, heavy program like FlightGear and need basically not much more than a window manager and X itself). So an alternate "light" desktop session type is nice to have.

There is the Xubuntu distribution of ubuntu, which uses Xfce. But I don't need to switch my whole linux install over. It's easy to add Xfce to an installed Kubuntu (or Ubuntu):

sudo aptitude update && sudo aptitude install xubuntu-desktop

I got this incantation from over here. This adds the packages for Xfce and puts a new session into your display manager's Session Type menu. If you had kubuntu or xubuntu and wanted GNOME as well you could install GNOME into either of them with the gnome-desktop-environment master package, I suppose. GNOME isn't my cup of tea.

I haven't played with aptitude yet, but you could substite agt-get for it in the commands above too I guess.

Yes, I know, Xfce is more than a window manager; it also has it's own file manager, terminal program, and so on. But the main feature is that it's fast and small, which matters most to me for it's purpose on my system.

2007-05-21T10:37+1000 Update RTFM again!

Since [k|x|ed]ubuntu is built upon Debian, all the documentation describing Debian packaging and tools (dpkg, apt-get, apt-cache, aptitude, dselect and so on) can be found at their site. The APT HOWTO is also probably a good place to start…