Ripping DVD Soundtrack to MP3
Audio-Only DVD Ripping Guide - How to Convert DVD Video to MP3 or Audio CD Format. A very useful guide that explains how to take the AC3 soundtrack and get it into MP3 format.
This is tricky because AC3 is at 48kHz whereas CDs are at 44.1kHz and are in different formats.
The key programs are "headaAC3he":http://mitglied.lycos.de/darkav/svcdguide/svcd.html (a wonderful name). This program downmixes an AC3 soundtrack into a Wav file. You can then use LAME or whatever MP3 encoder you want to convert to another format.