From Linux Journal
"Playing DVDs under GNU/Linux has not had the happiest of histories, what with the DeCSS debacle and subsequent legal battle. So you'd be forgiven for
thinking that you will never be able to play your DVDs on your GNU/Linux system. Luckily, this is not the case, and there are several applications
available for you to download and use. The issue with DeCSS is still with us but is slowly getting clearer. However, this has left some of the DVD
players officially not supporting encrypted DVDs, although unofficially, playback is possible via third-party additions.
This introduction to DVD playback applications for GNU/Linux looks at Xine, VideoLAN Client, MPlayer and Ogle. In addition to playing encrypted DVDs,
unofficially in some cases, several of these players also will play back other file formats."