If you're already planning to buy the PC version of Left 4 Dead, you might be interested to know Valve is running a great deal on its entire back catalog with the Valve Complete Pack. For a mere $100, gamers can score all 22 titles released within the studio's twelve years of development history, including every Half-Life game and Counter-Strike iteration, as well as Day of Defeat, Team Fortress 2, Portal, and the aforementioned zombie shooter.
Individually, that amounts to about $234 according to the company. With Left 4 Dead currently selling for $45, you're basically getting all of Valve's previous releases for $55. Those who bought the Orange Box last year already own the priciest stuff in this bundle, otherwise this sounds like a deal well worth investing in. More details including the full list of games available can be found here.