I usually use one of the following in linux:

mplayer -vc null -vo null -ao pcm:fast -dvd-device /path/to/dvddrive/or/isofile dvd://1
mplayer -dumpaudio -dumpfile audio.ac3 -dvd-device /path/to/dvddrive/or/isofile dvd://1

Change the 1 at the end depending which program number on the disk you want to rip