Legio Wargames offers Legio VI Julia Augusta, a set of free wargames rules for battles of the late Roman Republic and Empire (100BC to AD250). They’re designed for 6mm, where one 20mm x 20mm stand equals a cohort.
Rules: Ancients
Age of Heroes Bronze Age Rules
Age of Heroes is a set of free wargames rules for playing skirmishes in the Bronze Age.
Fleet of Battle Ancient Galleys Wargames Rules
Fleet of Battle is a set of free wargames rules for playing out battles between fleets of ancient galleys. Think Ben Hur. There also are several pages of free print-and-play galleys for use in lieu of lead miniatures. The rules require a knowledge of the commercial Field of Battle wargames rules.
Glory In The Arena Gladiator Rules
Glory In The Arena is a set of rules for playing gladiatorial combat with 54mm figures.
Pharaoh Rides To War
Pharaoh Rides To War is a set of rules for 20mm battles between Egyptians and Assyrians.