I've written a small input app, for when I was tracking my UCD, that writes to a google spreadsheet. It presents a grid of the cars and popup forms with an autocomplete field like the ones at http://gt5cars.net/used_car_searches/new I would have to test if it's possible to let anyone use it and save to their own google spreadsheet. Assuming I could set it up, would it be of interest? The one nice advantage to it is the autocomplete field... After a while you start to learn which parts of the car models narrow the choices fastest.
e.
Interesting idea, might be worth trying out. I haven't been devoting much time to it recently but if you're planning on doing it, i'll give it a go.