I'll add to/modify this post in the future, instead of starting new ones... Traditions?
The Humble RPG Book Bundle: Dungeons, Monsters & Dragons 5E by Frog God Games & Kobold Press
Bundles, monsters, and dragons. Oh, and dungeons, too! This new RPG book bundle [...] supports the Fifth Edition of everyone’s favorite roleplaying game – plus Pathfinder, Swords & Wizardry, and more. You'll score a virtual stack of maps, campaign guides, adventures, and more. So stop dragon your feet and get it already!
There are 3 tiers, 1, 8 and 17 dollars. I caught this one late. It has just over 6 days left.
Past RPG book bundles: