For a limited time, the Habet, Hoc Habet! Rules from Scale Creep Miniatures is available on a pay-what-you-want basis. These are designed for fast combat among Roman Gladiators, including campaign and gambling rules.
Rules: Ancients
Easy Rules For the Battle of Thermopylae
If the movie 300 has inspired the wargamer in you, but not enough to go out and paint 300 Spartans and a couple of thousand Persians, you might want to head on over to the Junior General’s site. There you will find simple rules and paper figures for refighting the battle of Thermopylae
An Hour of Valor Fantasy Skirmish Rules
An Hour of Valor is a set of free wargames rules for Fantasy Skirmishes.
Celtic Skirmish Game
From Warspawn Games: Celtic Skirmish, a combination miniatures / board game.
Nauta Ancient Naval Wargame Rules
Nauta is a set of free miniature wargames rules for playing out ancient naval battles. The files are hosted here: