The Steam Holiday Sale has just kicked off and there are plenty of great deals - some of the more noticable ones (running for the next 48 hours) are Civilization: Beyond Earth (-40%), Dark Souls II (-63%), Total War: Rome II - Emperor Edition (-75%) and State of Decay (-75%). 12 Hour deals include Injustice: Gods Among Us (-75%) and Styx: Master of Shadows (-50%). The first Community choice is between Hack n' Slash, Neverending Nightmares and The Amazing Spider-Man 2 - all are 40% off, but will be 66% off if they win the vote.
You should also check out how the new curator and filter system works as the Steam storefront has a personalised link to games that are discounted that may suit your tastes. We got a ton of indie titles so that sounds about right (what we mainly use Steam for).
You can check out the full list of 6266 items here.