I'm making up some PCs for the sample adventure that comes with the Eberron book, and the warforged barbarian I created was dredged out of a swamp by scavengers, tossed into a junk pile, re-activated, and stumbled into the forest, where he ended up literally being raised by wolves for a few years. I don't have specific geographical locations for all this to happen (haven't gotten that far in the book yet) but that's the basic concept. He's a feral robot.
I imagine that communities of warforged that spring up in wastelands would develop into barbarians. They might even seize on this as a reaction against the society that created them and forced them into battle. By destroying civilization, they think they can put a permanent end to war.
Also, the reavers from Firefly inspired me to cobble together some notes on malfunctioning, psychopathic warforged barbarian tribes that want to become human by wearing humanoid skin, bone talismans, and other nasty little accessories.