There are a lot of people out there trying to recapture the spirit of the original D&D games. For my own part, I can think of nothing that was more magical than my first excursion into the blue covered rulebook I got back in the late 1970s/early 1980s. Old School Hack is another attempt.
fantasy
Random Dungeon Generator
Here’s a nice random dungeon map generator. They have a very old school look.
Song of Blades and Heroes Solo Rules
Here are some interesting thoughts on playing Song of Blade and Heroes solo.
Solo Lord of the Rings Battle Game Rules
Isuldur’s Bane is the name of a free set of rules for playing Games Workshop’s Lord of the Rings Battle Game.
Three Plains 15mm Fantasy Wargaming
Three Plains is a free fantasy wargaming system. It also comes with free print-and-play figures.