Seems like the Valve Complete Package has been updated to include Left4Dead 2 now.
Counter-Strike
Released Nov 1, 200088$9.99
Counter-Strike: Condition Zero
Released Mar 1, 200465$9.99
Counter-Strike: Source
Released Nov 1, 200488$19.99
Day of Defeat
Released May 1, 200379$4.99
Day of Defeat: Source
Released Sep 26, 200580$9.99
Deathmatch Classic
Released Jun 1, 2001$4.99
Half-Life
Released Nov 19, 199896$9.99
Half-Life 2
Released Nov 16, 200496$19.99
Half-Life 2: Deathmatch
Released Nov 1, 2004$4.99
Half-Life 2: Episode One
Released Jun 1, 200687$9.99
Half-Life 2: Episode Two
Released Oct 10, 200790$14.99
Half-Life 2: Lost Coast
Released Oct 27, 2005N/A
Half-Life Deathmatch: Source
Released May 1, 2006N/A
Half-Life: Blue Shift
Released Jun 1, 200171$4.99
Half-Life: Opposing Force
Released Nov 1, 1999$4.99
Half-Life: Source
Released Jun 1, 2004N/A
Left 4 Dead
Released Nov 17, 200889$29.99
Left 4 Dead 2
Released Nov 17, 200989$49.99
Portal
Released Oct 10, 200790$19.99
Ricochet
Released Nov 1, 2000$4.99
Team Fortress 2
Released Oct 10, 200792$19.99
Team Fortress Classic
Released Apr 1, 1999$4.99
Individual price
$259.81
Package price
$99.99
Cost to you
$99.99
You save
$159.82