A huge sale on horror and horror-themed and random other games has begun on Steam just now, and there are lots of deal to be had.
Here are a few of the dozens of sale games:
Dead Space pack: $10
The Darkness 2: $7.50
Condemned: Criminal Origins: $3.74
Serious Sam 3: $6
Rise of the Triad: $7.50
Left 4 Dead 1 and 2: $7.49
Sleeping Dogs: $5
There's also the GOG sale if you're into the DRM-free thing.