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
From Warspawn Games: Celtic Skirmish, a combination miniatures / board game.
Blades of Bronze is a set of free wargames rules designed for short skirmish 15mm ancient wargames. The rules revolve around the ability of the leaders to give orders to the troops.
Roar of the Crowd is a set of free rules for playing science fiction, fantasy or historical gladiator games.