Best place to sell iPhone 4?

I'm getting an iPhone 5 around novemberish and I was wondering where the best place to sell my iPhone 4 would be. I scanned eBay real quick and 8gbs are going for $250-$300 and I have a 16gb and my dads got a 32gb.

Added (1). Btw, the "free" iPhones aren't unlocked. There actually around $1000 because of the contract. A brand new unlocked iPhone 4 8gb is $449.

Amazon.com trade in program

free to mail it to them and you'll get a amazon gift card as credit
and can "shop"

I don't know who in their right mind would buy a used iPhone 4 on ebay for $250-$300 considering that Apple is now selling iPhone 4's new for FREE.

I suggest selling it to Gazelle. Gazelle will recycle your phone. They make their money by selling recycled materials.

Here's a link: http://www.gazelle.com/iphone