I recommend Video-to-Video. free and converts from anything to anything.

File --> add DVD

then it should pop up a screen where you select the format you want to convert to. select the audio profile tab and then mp3.

I have not tried it specifically with DVDs but I use it all the time otherwise.

depending on the structure of the DVD you may end up with one file containing multiple songs. there are ways around that too but it may not be an issue for you