WolfSongX posted a really good guide which I used to do my doors and I couldn't be happier with the results.
http://www.ft86club.com/forums/showthread.php?t=28506
I didn't do full coverage with the butyl/aluminum component and just followed his method of tapping to find the resonances and covering as needed and it turned out great. The closed cell foam acts as a nice super sized gasket between the door card and door. No more rattles when listening to heavy bass music and the stock speakers sound 100% better.
As far as raw materials I went with Second Skin Audio products from the DIY guide above and ordered:
1 x Damplifier Pro (vibration damener) 13 sq. feet - Door Pack
2 x OverKill (closed-cell foam) 9 sq. ft
1 x Speaker Tweaker Kit
I still have one or two tiles of the Damplifier stuff left and some scraps of the foam which I have been using to fix various other rattles and noises.