Schlachtfield is less a set of free wargames rules than a series of thoughts about ancients wargames. It is interesting nonetheless.
Rules: Ancients
Trireme Game Rules
The Trireme Battles blog offers a set of free wargames rules for trireme battles.
Reconstructed Sweet Home Rules For Ancient Battles
Blunders on the Danube Blog has a set of free wargames rules for ancients battles based on Charles Sweet’s classic set.
Quick Ancients
Fr. Aelred Glidden, who was a frequent contributor to the late, lamented wargames magazine MWAN offers Quick Ancients, a set of free wargames rules for
Napnuts Masters of the Mediterranean Campaign
Masters of the Mediterranean is a set of campaign rules for ancients.