Fat Goblin Games has a moving sale, 95% of their stuff is on sale for $1 each. I am a fan of their Shadows over Vathak horror setting and there are some real steals here like the Forgotten Foes monster book and the Fat Goblin Guide to Hell. No idea how long this will be running.
5e Parents' Guide to Classes
Necromancer of Zhentil Keep (Adventurers League!)
Swords of the Moonsea (Adventurers League!)
Xanathar's Extraordinary Vault
Xanathar's Lost Notes to Everything Else
Thule 5e Sale this week. Primeval Thule 5e Campaign Setting goes from $19.95 to $9.97 and POD from $49.95 to $39.95 and the GM and Player Companions go from $7.95 to $1.99 each with POD from $17.95 down to $12.95.
There is also a Saltmarsh Sale at DMs Guild to promote the new 5e adventure Ghosts of Saltmarsh. The Sea Devils sahuagin sourcebook and Sea of Blood module from 2e are 60% off for $1.99 each, while U1-3 are 30% off for $3.49 each and there is a 5e guild bundle about 50% off on nautical adventures and options for $9.99
Goodman Games 3e Throwback sale All d20 PDFs are $1, $3, and $5. Tons of Dungeon Crawl Classics Modules (including the Castles and Crusades ones), the megadungeon boxed set one, the campaign setting, the Complete Guide to X line, DragonMech, Xcrawl, Broncosaurus Rex, Etherscope, and others. 1 week.
Humble Bundle 5e Beast of a Bundle a ton of 5e books from a variety of publishers with a majority from Frog God Games. 5e Tome of Monsters is the big one for me. Options at $1, $8, and $15 price points.