The first Left 4 Dead's DLC is on sale this week on Xbox Live for Gold Members. Normally setting you back 560 
, or about $7, the pack is on sale for 320 , or about $4. The content includes a new single player campaign mission with two levels that takes place immediately following the No Mercy mission.
No doubt this sale is getting those folks ready for the new DLC for Left 4 Dead 2, called The Passing, which will feature the Left 4 Dead 1 survivors meeting up with those form Left 4 Dead 2. We expect that package to hit on April 27th for the price of 560 . Of course the content won't just be a new campaign, but much more.
Source: Marketplace.xbox.com