There is a product that DuPont (at least used to) sell that is a peel and stick gooey gray substance held together between pieces of plastic. The installer just peels off one side and sticks the sheet to any clean surface in the car. One of my old GM cars had it in the trunk over the wheel wells. With age and heat some of the stuff would liquefy and run. A DuPont representative said that the automotive paint division sold it, and it was rather expensive for what it was. He told me of a demonstration that they would do by sticking a 1" square piece of the stuff to the bottom of a gallon paint can. He said that the sound deadening properties were great. It is useful to stick inside of doors between the inner sheet metal and the impact beam since this is a difficult area to get a good coat of rubberized undercoat applied without dripping it everywhere. Before the moderator kills this thread, I'll tell you of another soundproofing job I did to a stainless steel sink. Hey! It's soundproofing stainless, so it applies to this list, don't it? I used a can of that expanding foam insulation sold at home improvement stores. I applied a series of 1/2" thick beads of the stuff to all the under surfaces of the sink. As it hardened, it made a uniform 3/4" thick layer of foam insulation. Before I did this, the sound of water resonating on the bottom of the sink would drive me nuts. Afterwards, the sink was very quiet and kept the water nice and warm to do the dishes. I've thought about putting this stuff inside of cars, but it would be very messy unless you had a lot of room to work. In fact, I'm considering applying this stuff to the inside roof of my Delorean while I'm replacing the headliner. It would sound proof and also keep the car cooler -- a big plus in Florida. Walt Tampa, FL