Capturing screen action to a movie file, how?

[Gain Paolo Mureddu]

    I was wondering how easy would it be to do capture screen action to 
a movie file... What I want to do do is something similar to what Apple 
has done to show off their OSX where you can see some on-screen actions, 
like opening X or Y program, then switch tasks, etc, etc. I was 
wondering if there is a program for Linux (ok, for X) that would allow 
you to do exactly that, and then be able to transcode that into an .ogm 
file, for instance. If so what's that program and where do I get it??

I want to do a series of tutorials for my family, but instead of me 
being present at each computer, they could only open the file, see how a 
certain task is done and that's about it. You could say I want to do 
some Linux marketing too :-P