Tractorhouse.com provides prices for used farm equipment that includes John Deere, Massey, International and New Holland-brand tractors. The website also has listings for farm tractor parts and other farm classifieds.
Another source to use is IRON Guides, which is the farm equivalent of the blue book used for automobiles. It offers prices and details on tractor brands such as Kubota, New Holland and John Deere. In addition, the Official Tractor Blue Book offers information on the suggested used tractor price as well as what the equipment cost when it was new. It also lists nearly every tractor made from the 1930s to the present and is available through many online booksellers.