"I'm selling my D90 or D-whatever and such and such lens to buy a new D7000. How much would you pay for such a kit if I also include such and such accessory." Or,"do you think someone would pay me $XYZ for my D90 if it's in excellent condition and only 6 months old." Etc. Etc.
Don't start such threads. We don't allow buying or selling in the forum. Yes I consider such questions as advertising your gear for sale. If you want to know what your gear is worth check out ebay, keh, or your local craigslist and make your own informed decision. Your gear is worth whatever someone else wants to pay for it. Let's not fill the forum with "how much is my gear worth now?" posts.