a few details on the new zones we'll be visiting in Northrend. Of course, all of this is subject to change per developer whim but this is what Northrend is shaping up to be, so far. Salthem lists six zones (with notes that there will be more, though the exact number hasn't been finalized yet) that will be comparable in size to Outland zones.
Howling Fjord: Your first chance to go up against the ancient Vrykul in their instance Utgarde Keep.
Borean Tundra: The home to the Tuskarr. Parts of Borean Tundra are being melted down for water by the Naga. Garrosh Hellscream has established a base of operations at Warsong Hold.
Grizzly Hills: The home of Furbolgs and their city of Grizzlemaw. Also home to the ancient Dwarven City of Thor Modan. The land is largely covered in forests - an example of our desire to make sure that not all zones are just snow and ice.
Dragonblight: The home of Wyrmrest Temple, the ancient meeting place where dragons go to die.
Lake Wintergrasp: A new non-instanced PvP zone with Siege Weapons, destructible buildings and multiple objectives with lasting effects. Players on Normal realms will automatically be flagged for PvP when entering this zone.
The Storm Peaks: Containing Ulduar, the ancient Titan city in the Far North.
The capitol city of Northrend (the Shattrath of the north) will be Dalaran. Yes, you read me right, the same Dalaran that presently hides under a sparkly dome near Hillsbrad. The Kirin Tor have invoked powerful magic to relocate their city, and hopefully safeguard themselves from the dragon Malygos, who is concerned over magic running amok in Azeroth.