Best Buy, has revealed that they'll be accepting trade ins on a bunch of electronic products, such as Mobile Phones, Cameras, Camcorders, PDAs, Computers, and more. They've put together a website that gives you estimates of what your product is worth, and then allow you to process the estimate by sending in your product for a gift card with a prepaid shipping label. The steps are detailed on the website a bit more thoroughly, but that's the gist of it.
Videogames are, unfortunately, an exception. So you'll still have to unload those at EB, GameStop, Amazon, or eBay. But, videogame consoles are accepted, though for questionable values. A $200 estimate for a 'like new' Elite 120GB Xbox 360 and two controllers? No thanks. You can get far more on eBay; a quick search shows used Elites selling for over $300. So my personal suggestion is don't bother – go with eBay and get far more money there. Plus, it's better than getting a gift card.
If you'd like to entertain yourselves and do a few estimates, feel free to check out the website below.