My wife picked me up the latest issue of 2600 yesterday. They had an article about gamestop trade-ins that I thought I'd scan and pass along. Of course, my best advice with respect to trading-in games at major gaming retailers is: don't. You'll get a much more fair trade on kijiji or some local site.
Sorry the quality is crap, I scanned it as a 16 colour gif to keep the file size small.