All classic sites should look this good and be so comprehensive. Both dealer and private sales are offered. You can do it online with this site, which is west-coast based but expanding. New auctions all the time. Car Collector Excellent source for all who love collector cars.
Articles cover vintage cars, toy cars, automobilia, and the way it was.
For those who proudly mount club badges on their car, or even collect them, this Malaysian site is a lot of fun. You'll see dozens of badges, find interesting links. Although basically a commercial site selling accessories, CarLovers has the most complete selection of vintage car photos I've seen yet. A big site and a good one. If you ever thought about driving across America in a vintage car see The Great Race.