Commemorating QuakeCon 2010, Valve is slashing a hefty sum off a different title every day until Sunday. If you hurry, you can still grab yesterday's deal (66% off Oblivion GOTY), but if you miss it, 66% off the Doom Pack should cheer you up. The bundle includes Ultimate Doom, Doom II, Master Levels for Doom II, Final Doom, Doom 3, and Doom 3: Resurrection of Evil. Here's what's coming over the weekend and a few other sales currently on Steam:

Fallout 3 GOTY $25 (50% off, Saturday only)
Quake Collection $10 (75% off, Sunday only)
QuakeCon 2010 Pack $70 (50% off through Sunday)
Booster Trooper $5 (50% off)
Global Agenda $30 (25% off)
Numen: Contest of Heroes $22.49 (25% off)
RailWorks titles 50% off

More game deals after the jump. Impulse
Command and Conquer 4 $15
C&C Red Alert 3 $14.99
C&C Red Alert 3 Uprising $10
Trine $10
Gratuitous Space Battles Complete $26
Devil May Cry 4 $15

Direct2Drive
Stargate: Resistance $15
Amnesia: The Dark Descent $18

Good Old Games
Phantasmagoria bundle $11.18 (30% off)

EA Store
The Sims 3 $28.54
The Sims 3 World Adventures Expansion $20