I stumbled across this article today in a solicitation to subscribe to The Independent Review. Unfortunately the full article is not available online, so the summary below is all I can provide. I would like to read it, so if anyone can find it online or email me a copy of the PDF/doc, I'd sure appreciate it!

An Ancient Stateless Civilization: Bronze Age India and the State in History

By Thomas J. Thompson

The urban civilization of Harappa in southern Asia flourished economically and culturally for seven centuries, leaving archeologists with artifacts galore but with no evidence of wars or threats of war—or even a state. Most likely, Harappa’s archeological uniqueness has to do with the civilization’s having generated purely voluntary government.

Another such functioning anarchic society, for those interested in such things, is the Icelandic Free State of medieval Iceland, the anarchic private law nature of which was popularized by the self-described "anarchist-anachronist-economist" David Friedman (son of Milton Friedman). Here's an article of his on medieval Iceland: Private Creation and Enforcement of Law: A Historical Case. Another interesting article on the same subject is Roderick Long's "Privatization, Viking Style: Model or Misfortune?"

Another classic example is the so-called "Wild West" period of the American West. For a revisionist view of the Old West as an anarchic society, see An American Experiment in Anarcho-Capitalism: The Not So Wild, Wild West, by Terry Anderson and P.J. Hill, or their recent book, The Not So Wild, Wild West: Property Rights on the Frontier.

For more examples, see Historical Examples of Anarchy without Chaos