Car trading resources

Almost all car trading web sites follow the same pattern in their application design. There are three major sections in each, "buy", "sell", "tips" or "advice". This is pretty much straightforward. Bigger sites have also all kinds of tools such as "research a car", "find a true value" and the like. I'm talking about free tools to attract users to the web site, make them want to visit it again, not the tools that brong profit to an owner (vehicle history check, loan application, insurance).