I tend to hang around the Overclockers Austrlia (OCAU) only just for the Buy Sell Trade forums.
Reason being is that they are locally based. (Sydney, Australia)
The other thing that I like is that they have seperate FOR SALE, WANT TO BUY, PRICE CHECK and WHERE TO BUY sub forums.
Mind you, you need to be an active forum member for at least 90 days before you can create a new thread in the Selling Sub-Forum.
well i am like harper. OCAU is a great place to buy sell or trade, even if you are outside of australia you can sometimes get things. i also hang out at austech.info