in a mutliplayer
The Age of Empires Rise of Rome gives you four more civilizations.Roman, Carthaginian, Macedonian and Palmyran. It also has more units.
There is a add on called Conquest of the Ages made by Aztech New Media that has 4 very hard campaigns with Hittites, Phoenicians, Assyrians and Shang.
Everone is just waiting for Age of Empires II,Age of Kings. It is going to have all new units with all new buildings.