I'm reviving this thread to sticky, so for all new sales news (Adventure Shop, Steam, GOG, anywhere), please post here instead of starting with a new thread each time.
And to give it a kick start, Machinarium is now on sale from the
official website for only $5 until August 12th. If that sounds cheap, it's still $5 more than most people apparently paid.
This is Amanita's "Pirate Amnesty" sale, encouraging all the freeloaders to finally cough up some bucks for a game that's well worth it.