Keeping busy tonight, Valve Software has also announced that GSC Game World's critically acclaimed FPS/RPG, S.T.A.L.K.E.R.: Shadow of Chernobyl, is on sale for just $4.99US (a 75% savings) through Steam from now until Sunday, December 21st. So if you're looking for something to play over the Holidays, this is definitely a deal worth considering! ;)