There are a few that can give an idea. Also machinery trader has a search that can search auction results which can give you an idea of value. Tractor house and fastline can also search what dealers are currently asking. You won't get what they are asking, but it gives you a guide.
Never used either of these, but I have tractor house, machinery trader, and fastline.
http://www.ironsearch.com/PopularSearch/tractorbluebook.aspx
The Official Tractor Blue Book™
You need to subscribe to use these.
Only the 2 I linked to, the others are 3 I listed are free.
OP didn't ask for free, just if there were sites.
Thanks for posting the Links.You need to subscribe to use these.
IMO, the info we find in blue books is worthless as its based more on trend analysis than real pricing. Tractor house and such are often wish lists, not reality. I don't know of any source for the real world values we put to things.