In MA there is a dealer auction--ADESA located in Framingham, MA. In order to bid you must be a dealer (new or used). Each dealer must be registered and his account maximum is fixed. I have attended as a "guest" of a used car dealer many times when seeking a whole car vs a salvage. There are also luxury sales for "high-line" vehicles such as BMW, Lexus, Mercedes, etc. on specified dates. In my experience, most of the vehicles put through the auction either have high mileage or other problems. Those vehicles which are exceptional, tend to get the most attention and thus the price is often close to trade-in. The problem with an auction vehicle is that there is no warranty other than if some major problem is ID'd shortly after resale. You or the person bidding on the vehicle must be expert in autobody/mechanical repair as you may start the vehicle, check the trans in place, but that is it. The rest must be visual inspection. The auction house only lists a lot number, stock number, serial number, year, model, doors, color and mileage.
You can also determine the auction prices of pending vehicles by looking at the sales results of the previous months auction. This info is also available from the auction center and will provide year, model, mileage, and auction selling price.
Another source for a vehicle is your local banks and credit unions. They may be able to provide you a list of vehicles on which they are foreclosing or have already foreclosed upon.