I've seen people pull a lot of them out of their hat from time to time, not sure where people have been finding all the info. It doesn't seem to be well organized. (ex, I've seen people post how to adjust headlight angle via vag, but can't find it documented anywhere)

<a href="http://www.audiworld.com/tech/misc29.shtml">Linkydoo</a>

Don't know about a comprehensive list though...wouldn't mind finding one myself!