Tractor "Blue Book"...

[Fossil Farm]

The Successful Farming magazine has the Machinery Pete section. His auction results are from the larger real ag world auctions. Pretty interesting to follow the trends in ag equipment. Hot Line puts out equipment value guides, but again, they are just guides and it really depends on your area of the country on what realistic values are.

 

[gsmaneeley]

Tractor house is great you can search in your area. No sense seeing what prices are going for if they are 1500 miles away