The Battle of Chaeronea (338 BC) featured the Macedonians under Philip against a combined force from Athens and Thebes. The Junior General has rules and paper figures at the links.
Rules Link
Paper Wargames Figures: Link
Schlachtfield is less a set of free wargames rules than a series of thoughts about ancients wargames. It is interesting nonetheless.
The Trireme Battles blog offers a set of free wargames rules for trireme battles.
Blunders on the Danube Blog has a set of free wargames rules for ancients battles based on Charles Sweet’s classic set.
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