Noting the recent mention of LinDVD here, I thought the following
information might be of interest ...

There is a relatively easy way to get DVD playback working under linux (at
least it worked for me under Mandrake 8.0).  The complete_xine site
provides binary RPM packages for versions of the xine MPEG player that
include encrypted DVD playback capability:

http://gape.ist.utl.pt/ment00/linuxdvd.html

Xine was not too difficult to set up.  The hardest parts were setting up
the raw DVD device (see instructions) and figuring out that it was
necessary to upgrade the default Mandrake 8.0 kernel (used Mandrake kernel 
RPMs to upgrade from 2.4.3 to 2.4.7).

Xine 0.5.2 looks nicer, but appears to drop more frames and was unable to
play the last track (37) of The Matrix, so I'm currently using Xine 0.4.3
(had to manually delete the ~/.xinerc file when downgrading).  For a
rudimentary full screen mode (using 0.4.3 without Xv), simply use
Ctrl-Alt-KeypadPlus to toggle X windows into a lower resolution video mode
(X video modes are configured in /etc/X11/XF86Config or
/etc/X11/XF86Config-4).

Command used to successfully run xine 0.4.3 (uh-oh - running as root):
# xine -s -A oss &

This stuff may be old news to some people ... but I think it's great!

Joel