RPG Worlds $25 bundle has a lot of books. A mix of campaign setting and their adventures for 5E (some of them can be used in OSR games). A bit of Castles & Crusades, enough to get started playing. A few OSR RPGs though no accompanying adventures unless you repurpose adventures in this bundle.

The most interesting to me is the OSE Advanced Player's and Referee's Tomes. That's $30 regular price so $25 to get them in a bundle not worth it. The other stuff in the bundle doesn't really grab me.

D&D 5th Edition

Book of Ebon Tides (Kobold Press, 254pp) - splatbook about the plane of shadows
Endless Encounters:Dungeons (Pacesetter Games & Simulations) - encounter generator + sample mega-dungeon
Ultimate Bestiary: The Dreaded Accursed (Nord Games, 272pp) - monster manual of undead and cursed monsters
Ultimate Bestiary: Revenge of the Horde (Nord Games, 194pp) - more details about classic monster races
Vault of Magic (Kobold Press, 240pp) - lots of magic items

AK1 The Brain Gorgers Appetite (Gamehole Publishing, 38pp) - adventure
AK2 Into the Deep Dark (Gamehole Publishing, 46pp) - adventure
The Forbidden Caverns of Archaia (Greg Gillespie, 296pp) - mega-dungeon
Courts of the Shadow Fey (Kobold Press, 148pp) - a big adventure
Empire of the Ghouls (Kobold Press, 354pp) - campaign
Into the Unknown (Pacesetter Games & Simulation,s 144pp) - solo adventure
Tome of Beasts II: Lairs (Kobold Press, 80pp) - 14 standalone 1-shot adventures
Warlock Grimoire (Kobold Press, 300pp) - Issues #1-10 of Warlock zine

The Cities of Sorcery (Art of the Genre, 126pp) - double trilogy of adventures (also for AD&D 1E)
The Complete White Ship Campaign (Art of the Genre, 128pp) - 5 adventures + 6 mini-adventures + setting supplement (also for AD&D 1E)

The Blight: Richard Pett's Crooked City (Frog God Games, 886pp) - city setting
The Blight GM Guide (Frog God Games, 158pp) - city setting
The Blight Player's Guide (Frog God Games, 58pp) - system neutral, player-facing information
The Blight: Map Pack (Frog God Games) - 4 maps
The Tome of Blighted Horrors (Frog God Games, 124pp) - monsters plus rules
The Blight Pathologies (Frog God Games, 72pp) - seven short adventures
TB1 The Crooked Nail (Frog God Games, 36pp) - adventures set in The Blight campaign setting
TB2 Horror Sinks In (Frog God Games, 90pp)
TB3 Bloody Jack (Frog God Games, 80pp)
TB4 The Crucible (Frog God Games, 64pp)
TB5 Children of the Harvest (Frog God Games, 44pp)

The World of the Lost Lands (Frog God Games, 516 pp) - campaign for Necromancer Games and Frog God Games settings
The World of the Lost Lands 5E Rules Addendum (Frog God Games, 44pp) - 5E rules
The Lost Lands: World Map (Frog God Games) - possible also part of below
The World of the Lost Lands: Map Folio (Frog God Games) - world map + 12 regional maps

Southlands Worldbook (Kobold Press, 322pp) - a desert/Egyptian-themed setting
Southlands Player's Guide (Kobold Press, 80pp) - races, spells, equipment for Southlands
City of Cats (Kobold Press, 154pp) - city gazetteer and adventure collection set in Southlands campaign setting

The Eye of Chentoufi (Gaxxworx LLC, 36pp) - part 1 of an adventure trilogy
The Heart of Chentoufi (Gaxxworx LLC) - tournament adventure, part 2

Castles & Crusades

Castles & Crusades: Players Handbook (Troll Lord Games, 228pp) - rules-light fantasy rpg
Codex Germania (Troll Lord Games, 112pp) - splatbook supplement based on German myths

Codes of Aihrde Expansion: The Environs of Aufstrag (Troll Lord Games, 20pp) - mini-setting

C7 Castle on the Hill (Troll Lord Games, 18pp) - adventure
The Hallowed Ring (Troll Lord Games, 12 pp) - adventure
Stains Upon the Green (Troll Lord Games, 22pp) - adventure
Giant's Rapture (Troll Lord Games, 32pp) - adventure
Death in the Treklant (Troll Lord Games, 78pp) - 3 adventures

Other

Dead Men Tell New Tales (North Texas RPG Con, 36pp) - adventure for D&D B/X set in the Sea of Dread
Guilds & Orders (Troll Lord Games, 16pp) - system-neutral supplement

Phylactery #1 (Planet X Games, 48pp) - OSR zine
Phylactery #2 (Planet X Games, 48pp) - OSR zine, perhaps only two issues and done

Gangbusters: B/X Edition (Mark A Hunt), 64pp) - based on TSR's Gangbusters adapted to D&D B/X rules
Tall Tales (Mark Hunt, 96pp) - wild west-themed game based on D&D B/X rules

Rocket Age (Why Not Games, 256pp) - pulp sci-fi rpg using Vortex engine (attribute+skill+2d6 >= difficulty number)

Old-School Essentials Advanced Fantasy Player's Tome (Necrotic Gnome, 256pp) - Basic D&D retro-clone rpg
Old-School Essentials Advanced Fantasy Referee's Tome (Necrotic Gnome, 256pp) -