My questions involves separating audio off a dvd so that I can get it onto my mp3 player. I bought a set of workout dvds, but I want to be able to listen to them while I workout at the gym. I can get the disks onto my computer but can't figure out a way to just get the audio. Any ideas??

You can use a program to rip the audio off any DVD. For example, there's a freeware program called Jodix.

Jodix - Freeware converts DVD AVI MPEG WMV RM to MP3 or iPod Video

You can extract sound from a DVD, one track at a time or a chapter at a time. Some simple command line examples should suffice to demonstrate how this is done.

First thing you need to do is make sure you have lsdvd and transcode installed:

sudo apt-get install lsdvd transcode

A DVD in your DVD drive will probably be identified as /dev/dvd. Have a look at its table of contents with the lsdvd command

lsdvd

to find the track information, and the longest track

Output looks like as follows
libdvdread: Using libdvdcss version 1.2.5 for DVD access
Title: 01, Length: 02:32:44 Chapters: 26, Cells: 27, Audio streams: 02, Subpictures: 01
Title: 02, Length: 00:17:36 Chapters: 02, Cells: 02, Audio streams: 01, Subpictures: 00
Title: 03, Length: 00:00:11 Chapters: 02, Cells: 02, Audio streams: 01, Subpictures: 00
Longest track: 1

To capture the audio from the tenth chapter of the first title, saving it in ogg format, the command line is simply

transcode -i /dev/dvd -x dvd -T 1,10,1 -a 0 -y ogg -m track10.ogg

The arguments identify the input as /dev/dvd (-i), the type of input as DVD (-x), the title, chapter, and angle to encode, in this case being title 1, chapter 10, and camera angle 1 (-T), the audio track is track 0 (-a), the output format is ogg (-y, and the output filename is track10.ogg (-m).

generates mp3 output of chapter 20 from title 1

transcode -i /dev/dvd -x dvd -T 1,20,1 -a 0 -y raw -m track20.mp3

To extract the whole audio track of a title (all chapters) as ogg audio

transcode -i /dev/dvd -x dvd -T 1,-1 -a 0 -y ogg -m audiotrack.ogg

If you prefer WAV files, the following will do it

transcode -i /dev/dvd -x dvd -T 1,20 -a 0 -y wav -m track20.wav

Here is guide for extract audio from a dvd and convert to MP3
Can I Convert or Rip Protected DVD to MP3 ?