I know this is somewhat preemptive, but I wanted to throw it out regardless since I just stumbled upon it:
on Amazonl: Prototype + Prototype 2 + Radnet DLC for $9.99 starting Sunday, reportedly Steam keys.
Also, the deal is going to be even cheaper during some Gamespot show, supposedly starting tomorrow according to this.
Some more info can be found here
starting at the bottom of the page, talking about all this goodness
Dark Souls Weekend
on Steam, $26.79.
Death Rally Weekend
on Steam, $3.49.
Another future deal on Amazon (that'll be updated when active)
S.T.A.L.K.E.R.: Shadow of Chernobyl
Red Faction Guerrilla
Red Faction Armageddon
Individual Steam keys, except for Stalker and Guerrilla, but it's possible that they will be Steam keys.