Oe Retro-Clones
Delving Deeper
Dungeon Crawl Classics
Labyrinth Lord Original Edition Characters

HB Retro-Clones
BLUEHOLME Prentice Rules (PWWY)
Mazes & Perils

B/X & BECMI Retro-Clones

1e Retro-Clones

2e Retro-Clones
For Gold & Glory
Adventures Dark & Deep :: 2e as if GG had written it
Hackmaster :: 2.5e
Myth & Magic :: 2.5e

Other Retro-inspired Game Systems
Barbarians of Lemuria :: pulp-style swords & sorcery
Dangers & Dweomers :: compilation of old-school rules across various editions
Dungeonslayers :: rules lite; modern; old-school style play
Errant :: modern medieval fantasy, old-school design philosophy
Heroes & Other Worlds :: TFT-inspired
Blood & Treasure :: d20 SRD as an old school retro-clone
Fire & Sword :: by Raymond Turney, RQ co-creator
Lamentations of the Flame Princess :: Oe-like weird fantasy
Legends of the Ancient World :: TFT-inspired, rules lite
Mazes & Minotaurs :: Greek-inspired old-school RPG
Microlite 74 :: Oe inspired; modern ideas w/ early edition spirit
Microlite 75 :: 1e inspired; modern ideas w/ early edition spirit
MyD20 Lite :: Oe inspiration w/ OGL application
Pars Fortuna :: S&W gaming in an alternate fantasy "universe"
Red Box Hack :: red-box inspired in a wuxia asian-themed world
Red Box Fantasy :: BX inspiration w/ OGL application
Renegade - Corruption :: lightly remixes OD&D to appeal to new players, teenagers and young adults
Runeslayers :: based on aborted 90s edition of RQ
Searchers of the Unknown :: 1-page old-school rules
Siege Perilous :: based on Ultima CRPG games; adapts S&W rules
Wayfarers :: classless, skill-based adaptation of 1e
ZeFRS :: "generic" sword & sorcery based on 1985's Conan RPG