I think its fame almost precedes it to a point, but Death Frost Doom is a really great module, and playing it with a group that doesn't know it is a really tense and rewarding experience.
In terms of more recent stuff, Gardens of Ynn is really great, as is almost all of the stuff by Hydra Cooperative.
While it isn't a module per say, Veins of the Earth is probably the best game book I've ever read. It's really incredible.
There are a few "classics:"
Ten Foot Pole is one of the deepest repositories of reviews for OSR stuff (my own "Stjernheim" got absolutely obliterated by the critic, it was great!). Personally I like large toolkits rather than more linear adventures or situations. A lot of Michael Prescott's Trilemma Adventures are fantastic; Ben Milton's Patreon in a similar vein. Skerples' Tomb of the Serpent Kings is a great "starter" OSR adventure that teaches you how to play that style of adventure game.
The way I prefer to run OSR-style modules is more so introduce the characters to a problem with several obvious paths but no obvious solution. In other words, stick them into a chaotic or complex encounter with no "right" answer and let them figure it out. The classic of these are procedurally generated settings with random encounters or inspiration / mashup tables, hex crawls / point crawls, lots of factions, etc.
Please, please, please check out Patrick Stuart's Deep Carbon Observatory:
An ancient dam has burst, flooding the valley below. The landscape is a drowned devastation filled with the desperate homeless and the opportunistically predatory; the lake past the dam is drained, and the things it kept drowned are now exposed, and open ...
I love this adventure, as I love all of Patrick's writings. Its opening is a model for how to run human suffering amid natural disaster in an impactful-but-not-gratuitous way; it has to my estimation the most interesting / nastiest Rival-Adventurer-NPC-Party in all of D&D-esques; I've not seen a better intro adventure to an Underdark campaign, yet.
Throwing in another vote for Emmy Allen's Garden of Ynn -- an adventure set in an extra-dimensional garden / maze, done via tons and tons and tons of random tables.
Also for Dead Planet, by Sean McCoy, Donn Stroud, and Fiona Geist -- *the* cutting edge in terms of layout and information design for adventures.
I'd cite Jacob Hurst's Hot Springs Island -- another masterclass in information design. A complete hexcrawl bursting with stuff, but a breeze to read and refer to because it is written and laid out to be usable first and foremost.
Luke Gearing's Fever Swamp -- hexcrawl set in a swamp. This is the kind of adventure I want to make when I grow up. Crazy, how much stuff it gets done in, what, two-and-a-half dozen pages?
Jason Sholtis's Operation Unfathomable -- just fucking fun. Underdark adventure. Pulpy goodness, doesn't take itself seriously, full of stuff for players to prod and pick at.
