So there's a few places you should follow if you're looking for deals on that in general, mostly from Twitter - I'll start with those:

Cheap Ass Gamer
Wario64
Nintendeal

A couple other things you should look at not related to social media are IsThereAnyDeal and the Steam add-on for Chrome, etc. Augmented Steam which gives you an idea, in real time when on the site, if you've got good deals somewhere on any given game plus additional information populated on any given game page, etc.