mencoder is the companion of mplayer, the very nice open source video player. I can't tell you how impressed I've been with the robustness, completeness, and performance of mplayer. It is truly a great piece of code, so I guess it should come as no surprise that I also like it's companion mencoder. There are way to many options for me to cover even a percentage of them here, so I'm just going to cover the one command that I keep in my back pocket for use with mencoder. Before I encode anything, I figure out which track I want to rip by running

mplayer dvd://1

and incrementing the track number until I find which one I want. (use q to quit mplayer and look at the man page or /usr/share/doc/mplayer... for more key commands)

Next, I run the following command to rip the movie

mencoder dvd://1 -ovc lavc -lavcopts vcodec=mpeg4:vhq:vbitrate=1024 -vf scale=400:-2 -oac copy -o /share/movie.avi

Now this tells mencoder to take the first track (dvd://1) and encode it using libavcodec (-ovc lavc) with mpeg4 compression, high quality and a bitrate of 1024k bits (vcodec=mpeg4:vhq:vbitrate=1024). It also tells mencoder to scale the video to 400 pixels wide while maintaining the original aspect ratio (-vf scale=400:-2) and to just copy the audio track without compression (-oac copy). The file is output to "/share/movie.avi". Now this is quite a command and there's a lot of tricky stuff in here, so your going to need to hit the man page if you want to understand everything. The most likely things for you to be able to play around with are the track number of course, then maybe the bitrate (try 512, 256, etc) and then the scale (possibly even eliminating the scale if you want to keep it at the original resolution).