Right well I was after some music today and my mate linked me to this site: www.mediaconverter.org
The thing is it isnt one of those sites that just converts files for you.
You can enter a URL to a Youtube video then it will convert it to whatever format you want, Video OR Sound, and then you can download it!
Personally I love this as I often find remix's and mash up's of songs on youtube and I want to d/l it, but just the sound file...
Anyways check it out