Lochagos, at the Lochagos website has collected all of the postings that Jervis Johnson made regarding Warhammer Ancients Battles, on the WAB Ancients List. Lochagos cautions that, while these are not official rulings, they do provide some insight into JJ’s thinking.
Brumbaer has published AncientMaster, a free set of add on rules for Games Workshop’s Warmaster. There also are a number of army lists and links to other sites.
The Newcastle Quite Decent Ancient Skirmish Rules are a playable summary of a much larger set.
Tom’s Ancient Warfare Rules is a set of free wargames rules for the ancient period.
Imagine Image offers the freeHex Command Ancients Rules for miniatures wargames. The hex system is supposed to simplify things and speed play. You can play without a hex board if you want.