Pharaoh Rides To War is a set of rules for 20mm battles between Egyptians and Assyrians.
Caveman Clash is a set of free wargames rules for playing skirmishes between cavemen. There also are paper figures if you don’t happen to have cavemen available.
There’s been an update for the free basic rules for Impetus, a set of ancient and medieval wargames rules.
The Jackson Gamers offer Ancients By Ral, an ancients version of the venerable Rules By Ral system.
Previously a commercially published set of wargames rules, Ancient Empires now is available in a new edition as a free download.
From the Yahoo Site:
Originally published in 1990, significant changes have been made in almost every aspect of Ancient Empires. Popular basing for figures is now utilized, and the game now includes a point system and a conversion matrix for those familiar with the ‘DBM’ style of gaming.
If you have tired of the traditional �beer and pretzels� ancient games so common in the market place and you want more, take a look at Ancient Empires 2nd edition. With Ancient Empires 2nd edition you can get together for a small two to three hour battle using one of multiple figure scale options.