Ebay is great for that sort of research. I had a nice old Gibson Heritage that I decided to sell, and i had a freind who was interested. I wanted to sell it to my friend at a good price, but needed to be sure what a good price was ... so I looked for the value of similar vintage guitars, in simialr condition. I discovered that my particular model had a premium value as a collector's item (because collectors value those two+ years when this model reached its peak quality) - and then I decided it was worth 500 to 700 as a good used guitar, and I saw prices for that particluar model from 700 to 1400. I was already happy with 500, since it was more then I would have sold it for withput doing any research, so my friend got a good price, at about market price (not counting the collector's premium) and I got more then I needed to make the deal! Ebay helped me, but never was involved with the transaction!