There are lots of programs for ripping DVDs to hard drive, but BeSweet is one of the best programs I've found for transcoding audio from DVD's.

It can handle Dolby and DTS (if you have SurCode DTS Encoder), there are dlls on the site for VOB input and AVI input, and you can make mux files to split the channels and transcode to 5.1 WAV or 6 mono WAVEs