http://www.gamesas.com/topic/1419910-game-sales-and-deals-steam-gog-gamersgate-impulse-desura-etc/.

This thread is for the discussion of gaming deals found on http://store.steampowered.com/, http://www.gog.com/, http://impulsedriven.com/, http://www.desura.com/, and other sites or stores.

See also the http://www.gamesas.com/topic/1398244-unofficial-is-insert-game-name-here-any-good-thread/, for advice on games you're considering.