There's a special promo for STALKER Call of Pripyat on Steam 19.99. Support you small developers!

Buy S.T.A.L.K.E.R.: Call of Pripyat Loyalty Promo
Loyalty Promo grants a discount off Call of Pripyat if you already own the Steam Version of S.T.A.L.K.E.R. Clear Sky or S.T.A.L.K.E.R. Shadow of Chernobyl. Please note that you need to have Clear Sky or Shadow of Chernobyl registered to your Steam account before purchasing Call of Pripyat to receive the discounted price.

The Weekend Deal is Mount & Blade at $4.99