aljundi if it's to check prices you can try elmazad.com (there are other websites but this is the one I know).
Example:
http://www.elmazad.com/item/iphone-3gs-32gb-white/72775
I got an iPhone 3G from a shop in Achrafiyeh last year. Maybe he would buy too.
As for me, I would sell my iPhone 3G 8GB, and add $150 to it to get a 3GS 32GB. That's how much I'm ready to pay.
My 3G is in good condition, just 2 barely noticeable scratches on the glass, a very small crack on the bottom plastic, and light scratches on the back (which is protected by a cover). I'm guessing you're not interested in exchanging (?) then I will have sell it first. I'm a bit lazy for doing that...