You know you have one of these babies laying around. Why not just give it up?
Many phone service providers, like Sprint, will take your used cell phone and related peripheral items. EcoATM has kiosks throughout the United States which will give you instant cash for your cell phone or mp3 player. Cell Phones for Soldiers will accept your gently used phones and use the money to provide soldiers with international calling cards so they can call home. Mail in Mobile will buy a large variety of used phones, even heavily damaged ones. Staples offers online quotes for the trade-in value of your device, but will still take it if it’s a valueless piece of crap.
In the UK? Try O2.