While many sites offer Buy and Sell forums, a new site called Pocket Classified is completely dedicated to buying or selling gadgets. You can sell your used gadgets by listing it (it’s free) on the classified related to the gadget you want to sell. You can also find a gadget to buy by browsing the classifieds below. The site includes RSS feeds so that you can keep an eye on categories of interest.
The site is new so there are only a few ads there now but hopefully it will pick up steam and offer more options soon!
Source: Pocket PC Thoughts