Basic Information from Blizzard regarding Undead:
Having broken free from the tyrannical rule of the Lich King, a renegade group of undead seek to retain their own free will while destroying all those who oppose them. Known as the Forsaken, this group is dedicated to serving their leader, the banshee queen Sylvanas Windrunner. These dark warriors have established a secret stronghold beneath the ruins of Lordaeron's former capital city. Situated deep beneath the cursed Tirisfal Glades, the labyrinthine Undercity is a sprawling bastion of evil. Within its shadowy confines, Sylvanas' royal apothecaries scramble to develop a devastating new plague - one which will not only eradicate their hated Scourge rivals, but the rest of humanity as well. To further their dark aims, the Forsaken have entered into an alliance of convenience with the primitive, brutish races of the Horde. Holding no real loyalty for their newfound comrades, the Forsaken have duped them into fighting against their common enemy - the Lich King. Only time will tell how these disciples of doom will fare in their mission of vengeance.
Start Location: Tirisfal Glades
Home City: Undercity
Available Classes: Warrior, Warlock, Mage, Rogue, Priest
The TenTonHammer take on Undead
Unlike the shambling zombie impression the Undead may first give off when you see them, as a race they are one of the more enigmatic choices you can start with on the side of the horde. With an interesting story background behind them, the Undead seem to almost be a “third side” in WoW.
Starting in Tirisfal Glades, the Undead start off by exiting a mausoleum, a rather creepy way to start off. From there the Undead continue the trend of darkness and gloominess with hunting down scavengers that surround the local area. Eventually you will reach the grand Undercity and can make your own way in the world.
Links to information on other WoW sites
Blizzard WoW site - The official Blizzard WoW Undead information page.