I'm going way back in time for this "fringe" period - the Ancient Greeks. Although not as seemingly popular as the Romans, the Greek reenactors still hold their own. The Hoplite seems to be portal of choice when it comes to this period. This site gives the reader a high-level overview of reenacting the Ancient Greeks, but also provides author information on some recent books of the period.
Another site of note is Matthew Amt's Greek Hoplite Page. Not as professional looking as The Hoplite, it does contain more information pertient to reenacting the period.
Although not Greek, but comtemporary to the Ancient Greek period, is the Hallstatt period reenactor's page, or Hallstattzeit. This is a German site with no English translation - but don't let that stop you from surfing it. Has plenty of great photos of a little-known sub-period.