I had this question also....I like vobcopy, it uses libdvdread..put your dvd in the drive change directory to a dir to put file in, then in terminal type vobcopy -l ,use the "-l " this will copy the movie as a single .vob file you can watch in the players.
http://freshmeat.net/projects/vobcopy/ alternatively you can use the built in mencoder to make an .avi file although I have less success with quality being a novice user of mencoder. but the file would be smaller...something like this I think
mencoder dvd://1 -chapter 1-? -o name.avi -oac pcm -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1000:vhq:vqmin=2:vlelim=-4:vcelim=9:lumi_mask=0.05:dark_mask=0.01:vpass=1
(you may need to do some googles)
http://web.njit.edu/all_topics/Prog_Lang_Docs/html/mplayer/encoding.htmlas above- you may aquire a copy of the bonus disc for gui programs of this nature
hope that helps