Arok-caid-This is a civilization of robots out to conquer. Apparently they uses to be a living civilization, as they have a giant brain as an overlord. Their most powerful unit is a completely customizable turret.
Zer Vor-These are militant aliens with plasma technology, but like to use destructive melee attacks, too. Mostly inspired by Halo.
Forces of Evil-These are the evil things: Goblins, Orcs, Wargs, Dragons, etc.
Medieval-These people use Swords&Sorceries to get the battle done.
Romans-Set to conquer the world Age of Empires style, except that they are the only civilization that builds in groups. Don't worry, their cheap, multi-functional catapults will work wonders against tanks and airplanes. They have other defences agains tanks, too.
Spy Civilization-I haven't done a lot with them yet, but for all you people who love converting units, this is it.