PlayTrade is a good service and unlike eBay, your listings stay up a lot longer. You just set a price and wait until someone buys it at that price. I've had a few instances on eBay where I've let some items go too cheap due to the auction format.
There are a lot more "casual" buyers on Play.com and you'd be surprised at how much they pay for something sometimes too. Sorry I took a while to respond.