Steam is offering the Valve Complete Pack for a good price.

Regular price is $99.99

Counter-Strike Global Offensive / Source / Condition Zero
Portal / Portal 2
Left 4 Dead / Left 4 Dead 2
Team Fortress Classic / 2
Day of Defeat / Source
Half-Life 2 / Deathmatch / Lost Coast
Deathmatch Classic

Link to Download for $24.99