While I predominantly use KDE on Kubuntu 10.10, I like to have a couple of other lightweight desktop environments installed so that I have graphical options if anything happens to my KDE installation (as sometimes happens when upgrading KDE).
I installed WindowMaker and LXDE as my alternatives, however, doing so also added KDM session entries for Openbox and KDE/Openbox, and I'm not interested in those.
Removing those entires is relatively simple. Open a root shell, open the files in a text editor (I like nano for simple jobs), then add the line "Hidden=true" to each of the files.
nano /usr/share/xsessions/openbox.desktop
nano /usr/share/xsessions/openbox-gnome.desktop
nano /usr/share/xsessions/openbox-kde.desktop
