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.
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 is a set of free wargames rules for Fantasy Skirmishes.
From Warspawn Games: Celtic Skirmish, a combination miniatures / board game.