Castle Triskelion is an old school fantasy role playing mega dungeon. It’s an ongoing project, and many of the pieces are available for downloading now, including what I have found is the most rare of modules — those for a small group of low-level characters.
Into The Fray Core Rules
Into The Fray is a set of free wargames rules for fantasy skirmishes. The authors write:
Designed so that each player will field between 15 and 20 figures in a standard battle, a game of Into the Fray will last about 2 hours with experienced players. The game includes rules for the standard fare like movement, combat and morale, and also includes a system for magic and special abilities that will keep things interesting even for veteran players.
Available only in an electronic format, ITF is a print and play game. It keeps the initial cost down and allows you to make as many or as few miniatures as you need to form your army. With a few supplies (cardstock and glue sticks) and a few hobby tools (a hobby knife and a straightedge) you can build all of the cards, miniatures, counters and templates you need. Add in a handful of six siders and a tape measure and you will be ready to get Into the Fray!!
War of Ashes: Shieldbash
War of Ashes: Shieldbash is a fantasy game set in a dying world. While the full game is a commercial product, the company offers the rules sections of the gamebook for free.
Middle Earth Skirmish Rules
Middle Earth are a set of free wargames rules for skirmishes in JRR Tolkien’s fantasy worlds. The set includes specific rules for battles in the three “Ages.”
Shield Breaker Fantasy Rules
Shield Breaker is a set of free wargames rules for fantasy skirmish. The authors write:
Shield Breaker is a game about warbands battling it out in a world of legends. It is intended for use with about 6–20 miniatures in the most common 28mm scale. Buy, borrow or steal any fantasy miniatures, compose a warband and you are ready to play.