General
Auction Air
Auctioning4u - eBay resellers
Auction Zone
Bullnet Auctions
Centaur Auctions
Morgan Auctions
Star Bids

General Person to Person
Amazon
EBay
EBid
Exchange Masters
QXL

Collectibles
Compal Comics - Comic books
London Art - Art auctions
Numismedia - Coins (U.S. based)
Sanda Fayre - Stamps
Stanley Gibbons - Stamps
Sweet Briar - Paperweights
Tramps UK - Memorabilia
Vectis - Toys