Let me give you some knowledge here, this thread is a bit ridiculous.
#1) Manufacturers of hitches - there are really only two - Uhaul and Drawtite/HiddenHitch/Curt (they will often have different part numbers but are the IDENTICAL product).
#2) Methods of installation - hitches for cars typically come in two varieties depending on your car - either they install by clamping or bolting to existing framerail connections (ideal) or by drilling holes in the spare-tire well and clamping to it (pretty poor). It depends on your model and there really isn't much you can do about it - an Acura RSX gets a hitch drilled into the spare tire well, a VW GTI bolts onto existing framerail connections. Therefore, the framerail models are removable without any permanent damage while one that requires drilling would leave holes that would have to be sealed.
#3) Installers - the process to install varies by model but most of these installs are dead simple and pretty much any shop could do it easily. You can phone pretty much any hitch shop and just get an installed price and go to the cheapest one, they are all pretty much the same stuff. I personally would much rather install it myself as there is a little room to make a mess if they aren't careful and don't take care with your car, especially if they were drilling into my spare tire well.
Go to
Trailer hitch, hitches and bike rack (800)298-8924 and look up what is available for your car. Then start phoning around.
Mark