As Jessica Dolcourt explained, turning an old device into cash is a fairly simple process. Not only does it eliminate clutter around your home, but it gives you extra funds to invest in that new device you've been drooling over.
Even if the return on an old device isn't a big amount, taking the time to turn devices into cold cash is well worth it.
One of my favorite uses for an old iPod Touch is using it as a remote for an Apple TV. Anyone who owns an Apple TV can attest to how easily the Apple remote is lost. An iPod Touch or an old iPad Mini is a bit harder to lose, and gives you a keyboard for those long search queries. The Remote app is free on iTunes.