What kind of adventures are you looking for?
Dungeon Crawl Classics RPG has tons of really cool thematic ones, but the theme is often gonzo 70s fantasy of Courts of Chaos, crashed space ships, serpent folk stuff and such which I find really great but is not to everyone's taste. Also Appalachian fantasy, Lankhmar, and Dying Earth.
Lamentations of the Flame Princess is a fairly B/X OSR system with a ton of adventures that vary considerably in tone including a number that are fairly harsh killer dungeon/adventure types sometimes with an adult content theme that is not for all audiences/tastes.
Castles & Crusades has a ton of adventures, most in the shorter range that are fairly standard D&D, a few Norse themed ones as well.
Hyperborea/Astonishing Swordsmen and Sorcerers has a number of Conan themed adventures. The system is mostly 1e with Conan type stuff instead of Tolkien races and D&D classes.
OSRIC is 1e OGL rules with a number of 3rd party publishers, Expeditious Retreat Press is notable for having a huge series of 32 page-ish adventures and the massive megadungeon
Arden Vul.
Old School Essentials (OSE) and Labyrinth Lord are B/X retroclones with options to throw in AD&D classes and monsters and races and such with a metric ton of adventures by numerous publishers.
Swords & Wizardry is an Oe retroclone with a ton of adventures as well, a lot of Frog God stuff so lots of
Rappan Athuk megadungeon and simiar themed stuff of hugely varying lengths but also the Norse mega-adventure path the
Northlands Saga Complete and the pirate horror themed
Razor Coast.