1. eBay is a the biggest of person-to-person auctions. Items are sold by an individual or business. They provide a feedback service where buyers provide feedback on their experiences with particular sellers. Lots of used BMW's and memorabilia for sale. Click here for a BMW search.
2. Yahoo has one of the bigger person-to-person auctions, and growing all the time. Yahoo Auctions offers a wide variety of items. Some of their services offered are a newsletter, calendar and message board. Yahoo Auctions is free to all users. Click here for a BMW search.
3. Amazon is a person-to-person auction, with a wide range of products from collectibles to sports equipment to computer and electronic products, etc. There is a Cars and Transportation section.

Looking for a new car? Click here for where to buy.

Looking to buy or sell a car? Here are some sites where you can go to buy or sell BMW's and other makes.

AFundRaiser is a merchant auction site that provides charity fundraising auctions for such charities as Habitat for Humanity, Jeff Gordon's & Ray Evernham's 'Racing for a Reason', and The Hendrick Marrow Foundation.

Auction US is a person-to-person auction house featuring a wide range of items. There is an Automotive section.

Audiogon is a person-to-person auction specializing in high-end audio gear. There are good deals to be found on some of the finest components available. 

Autobytel is a person-to-person auction for cars and trucks. Each vehicle up for auction has been professionally assessed and every vehicle sold comes packaged with roadside assistance. They have a section for research for buyers.

Autoweb is a car auction that features 1996 and newer cars. All cars come with a 3 month/30,000 mile limited warranty and a 72 hour, 300 mile money back guarantee. All vehicles sold have less than 60,000 miles on them and they provide an escrow service for buyers. They also feature a research section for buyers.

Bidder's Edge is a search site where you can search for items across several auction sites. Searches Amazon and Yahoo auctions.

GearHeadAuction is a person-to-person auction dedicated to power sports. It is free to use for buyers. It features cars, trucks, motorcycles, ATVs, trailers, snowmobiles, etc as well as parts and apparel. They are based in Michigan.

Swapman is a person-to-person auction which started out with Ford parts and cars but has branched out to include more makes and models. Swapman.com combines the excitement of an auction, the thrill and discovery of a good swap meet and the immediacy of the Internet. They are all cars, all the time. 

Transport Universe. All kinds of vehicles can be found at this auction.

WebCharity. Hundreds of charitable organizations use WebCharity auctions to turn donated goods into operating funds. You can support your favorite charity here.