S.T.A.L.K.E.R.: Shadow of Chernobyl and follow-up S.T.A.L.K.E.R.: Call of Pripyat are bundled together for only $10 on Steam through Monday. (The S.T.A.L.K.E.R.: Clear Sky prequel game is not part of the bundle; but it's is available separately for $10 on Steam.)
The full-on S.T.A.L.K.E.R. 2 sequel was recently announced and scheduled for release in 2012. While that gives you plenty of time to get to caught up, this weekend Steam sale might just be the excuse you were looking for to book your first trip to Chernobyl. That whole nuclear meltdown incident made it quite a lovely place for scavenging, trespassing, adventuring, loner-ing, killing, exploring and robbing. See what we did there?