http://slickdeals.net/permadeal/56573/ebay.com-xbox-live-4000-points-card
4000 ($50 worth) MS Points on sale for $40 shipped. They're going fast.
This is where I've gotten the last 12000 or so of my points. It's not the steepest discount I've gotten, but it's the steepest still available.
Don't say I never told you where to get discount points. ;)