The GM's Day Sale is on at DrivethruRPG, and will be on through March the 13th. Here's the OSR offers I recommend.
Whether you've never played OSR games, or you're a veteran looking for something cool, here we go!
OSR GAMES: THE BIG ONES
Worlds Without Number - Kevin Crawford's masterpiece, and one of the most successful games on the whole DrivethruRPG platform. A great game in itself, and a book with tons of tools to generate everything, from world building to adventures, whatever game system you prefer.
Old-School Essentials - Whole Line - The best retroclone around, a faithful reproduction of the B/X D&D rules, with an exceptional work done on the text to make it clear and user-friendly, with an egregious layout. Recommended if you're new to the OSR and want the distilled, simple experience of the original B/X rules. Everything you need to play in one book. Also, my favorite OSR game.
Dungeon Crawl Classics RPG Core Book - A glorious OSR game that is not a retroclone but captures the feel of old school games, with unique mechanics that build on a solid d20 system, generally compatible with other OSR stuff. Recommended if you want a more modern cut, while true to the spirit of OSR... and you like crits and fumble tables.
OTHER OSR GAMES
A lot of supplements and adventures are included in the GM's Day Sale!
The Gardens on Ynn - A point-crawl adventure set in an ever-shifting extradimensional garden, with a system to generate content while you play.
The Stygian Library - Gardens of Ynn's twin, this time a dungeon set in an infinite, extradimensional library.
The Black Wyrm of Brandonsford - An EXCELLENT sandboxy point-crawl adventure for characters level 1-3, very easy to run, with lots of interaction between locations.
Gotta review this sooner or later! Just reviewed it!
Puzzle Dungeon: The Seers Sanctum - Another very good 10 room dungeon with, well, a lot of well conceived puzzles!
Xanadu - Another acclaimed third-party Old-School Essentials dungeon adventure, by Singing Flame.
Bottomless Pit of Zorth - Another acclaimed adventure, with a slime theme and insane art, for characters level 3-5.
OR REAL OLD SCHOOL?
The sale is on a lot of actually old titles! Here's a few titles I recommend:
The whole B1-B12 series of adventures is on sale, with some must-have scenarios for the Basic D&D set. Note that the current sale makes them cheaper than the regular bundle with the all series!
So if you want to only pick up a few, I'd go with those that are the best in my view: B1 In Search of the Unknown, B2 The Keep on the Borderlands, B3 Palace of the Silver Princess, B4 The Lost City, B7 Rahasia, and B9 Castle Caldwell and Beyond with its five mini adventures.
And then there's a little less known supplement that's worth checking:
AC10 Bestiary of Dragons & Giants - Despite the "Bestiary" in the title, this is, for the most part, an adventure anthology with a dozen or so quick scenarios involving, of course, dragons and giants. A great pick for sandbox campaigns!
ALSO OF NOTE: 500 rpg items for $5 on itch.io!
On itch.io there's a great charity bundle with almost FIVE HUNDRED rpg items (full games as well as scenarios, zines and accessories) that's only $5. Among other things, it includes the Wyrd Science magazine issue 1 and 2; the Into the Wyrd and Wild setting; Planar Compass issue 1; the OSR adventure Roseate Growth; the OSR-compatible mini-game for spell research Vade Arcanum; the OSR dungeon adventure Sea Fortress of the Yule Queen.... and who knows what else! Definitely wroth checking!
Into OSR? Check my other OSR posts!