The GOG fall sale has started. There are new deals each day and you can level up to unlock games for free. Currently Little big Adventure 2 is also free which you can get from the homepage, only available for the next 48 hours.
More info here: https://www.gog.com/news/make_way_for_the_monstrous_fall_sale
Every $1 spent gives you xp, and "you can score even more free games during the Monstrous Fall Sale: participate in the fun, collect badges, and keep shopping to earn XP and unlock:
Some of the day 1 deals:
Stardew Valley £8.19
Rebel Galaxy £5
Witcher 3 GOTY edition £20.99
Master of orion (new one) £13.89
Quite a few others for todays deals and lots of other games on sale throughout the site.
Some of the bundles for day 1 include:
Deep Silver BYOB
Double Fine bundle