Recommended retroclone rules

• Basic Fantasy BFRPG
• The Black Hack
• Whitehack
• Delving Deeper (Immersive Ink)
• Beyond the Wall and Other Adventures
• BLUEHOLME Journeymanne Rules
• Astonishing Swordsmen and Sorcerers of Hyperborea

Great Free systems

• Grey Matter and Grey Six
• Swords & Wizardry rules for Core, Complete, White Box, and Light. In PDF and RTF formats.
• OSRIC - emulation of AD&D 1e as a massive tome. Contains a very complete list of classes, races, creatures, spells, and lots of dungeon generation tables. Monsters of Myth

Sci-Fi Retroclones

• Terminal Space - free. Modifies B/X D&D rules or Labyrinth Lord rules into a space setting.
• Starships & Spacemen 2e (Goblinoid Games)
• Stars Without Number (Sine Nomine Publishing)
• X-plorers (Dave Bezio)
• White Star
• Mutant Future
• Hulks & Horrors
• Space Ryft - setting and rules from Wizardawn magazine. Based on rules from Broken Urthe

Recommended Setting Supplements

• Slumbering Ursine Dunes (Hydra Cooperative)
• Ride Tide (Sine Nomine)
• The World of Glain (Chris Gonnerman)
• Mystara / Known World (TSR)
• Dwimmermount (Autarch)
• Yoon-Suin
• Castle Gargantua

Others to check out

• Realms of Crawling Chaos (Goblinoid)
• Mutant Future (Goblinoid)
• Ruins of the Undercity (Kabuki Kaiser)
• Operationg Unfathomable (Hydra Cooperative)
• Strange Stars (Hydra Cooperative)
• Weird Adventures (Hydra Cooperative)