Most of us probably have half of these, but if you don't, it's a pretty solid deal, especially if you were going to pick up Left 4 Dead ($44.99 alone). Steam digital download for $99.99.
http://store.steampowered.com/sub/1134
http://store.steampowered.com/sub/1134
Counter-Strike
Counter-Strike: Condition Zero
Counter-Strike: Source
Day of Defeat
Day of Defeat: Source
Deathmatch Classic
Half-Life
Half-Life 2
Half-Life 2: Deathmatch
Half-Life 2: Episode One
Half-Life 2: Episode Two
Half-Life 2: Lost Coast
Half-Life Deathmatch: Source
Half-Life: Blue Shift
Half-Life: Opposing Force
Half-Life: Source
Left 4 Dead (not yet released)
Peggle Extreme
Portal
Ricochet
Team Fortress 2
Team Fortress Classic