Most guides trade-in anywhere from $.20 - $2.00 at game stores like Play N Trade. I don't know of any websites that accept trade-ins, shipping would kill that possibility. Your best online bet is half.com or Ebay, be wary of site fees, shipping, and paypal fees. Your best local bet is a big warehouse style used book store. I can get up to $3 or $4 for new guides for store credit. Drive around and see what is on their shelves, if they have a lot of good new guides, it's likely they give good credit too.