new deal at Amazon's recently opened Xbox Live Store. Right now, if you purchase 4000 Microsoft Points, you'll get $10 in credit on future purchases. Essentially, it's like getting another 800 points. For those that can't pony up $50 for the 4000 points, Amazon is also offering $5 in free credit for purchasing 1600 MS Points.
It's not exactly a killer deal either way, but it should nab an extra XBLA game or at least some DLC down the road. Regardless, given XBLA prices lately, you'll need all the points you can get.