Lucky Day
Daywatch
Maybe check their front/home page at www.gog.com, where it shows you all the "thingymabobs". I'm trying really hard not to be sarcastic here, finding this isn't hard or complex or time-consuming.
On their homepage they not only show you the sales but even let you click to filters for things like quote "Roleplay", "Adventure", "Action" etc game types. There is also an ever present list for "Popular", "New", "Up Comming" and get this "On Sale".
Said homepage also has a link that will show you everything that's currently on sale
http://www.gog.com/games##sort=bestselling&price=discounted&page=1
Though that won't show you bundle deals which are, again as a reminder, on the illusive homepage, top and center.
I know many people expect to be spoonfed, but for heavens sake what more could one expect them to do short of physically coming to your house to recite this verbally.
For heavens sake man, it's all right there on a single webpage, their homepage. This could not be easier if they made an instructional video which would be 5 seconds long with someone demonstrating how to type "gog.com"
LOL - you're right. For some reason I thought the news feed was their homepage.