Hmm, I think Valve are starting to get cryptic with their registry names now. Some of the latest ones:
Eidos Montreal Dev Comp - not sure what this is, both DXHR and all its DLCs have entries already.
Turbine Autogrant Comp - no info on this one either.
New Bethesda Game - again, no info yet.
Some recent additions that do have some information - seems that there will be a Trine 2 beta. There's some Dungeon Defenders pets. Cave Story has been added, also there is a "Chapters DLC pack" and a "Complete DLC pack" for DoW II: Retribution.
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Sword of the Stars Complete Collection is 75% off too. The sequel is out in just over a week, so that's likely why they've discounted the first game.