Knowing that touch-up is never ideal, I tried this system and was impressed enough with the results on my wife's car to forgo about $2,000 in "new paint".
http://www.drcolorchip.com/
Here's a review from the Wall Street Journal.
http://www.marketwatch.com/story/a-do-it-yourself-facelift-for-the-car
One caveat -- and they clearly note this on their site, for some reason touch-up on silver cars (my Boxster is Artic Silver) -- is particularly difficult. But I tried it on my car anyway. Less pleased with the results (as they predicted). But on my wife's dark blue Mercedes, it did a fantastic job. If you have a dark car -- or anything non-silver for that matter -- it's really worth a shot.