Valve send word that The Sacrifice, the DLC for both Left 4 Dead and Left 4 Dead 2, is now available on Steam.
"The new DLC is available free of charge to all Steam gamers who own a copy of L4D and/or L4D2. And, for a limited time, L4D and L4D2 (as well as their respective Steam bundles) are available for 66% off the regular price."
That said, my Steam doesn't seem to be updating. Hmm. Oh, now it is.