"Amazon is upping the ante against Gamestop with their latest promotion.
Trade in any four games through Amazon.com's Video Games Trade-In store before April 12, 2009 and in addition to your Amazon.com Gift Card, you'll receive $20 off a select new release title in the Video Games store.
Don't have 4 games you want to trade in? Trade in any two games before April 12, 2009 and you'll receive $10 off a select new release.
The participating titles to choose from are listed on their site..."