While it wasn't listed among the other Valve games that were getting Mac OS X support earlier today, the original Left 4 Dead is also making its way to Apple computers alongside its sequel.
The official Left 4 Dead blog confirms that Francis, Bill, Zoey, and Louis will be hitting the Mac platform this spring, right alongside Portal, Half-Life, Counter-Strike and Team Fortress 2. And, like all the other games Valve is giving the Mac treatment, the original L4D will be cross-platform compatible, meaning Mac and PC users will for once have to find common ground in order to survive.
Left 4 Dead 1 and 2 are coming to the Mac! [L4D Blog]