Utgarde Keep

Dungeons: Utgarde Keep (70 - 72), Utgarde Pinnacle (80)
Located in the Howling Fjord, Utgarde Keep features two different 5-man wings - Utgarde Keep, which is catered to level 70-72 players as an entry-level expansion dungeon and Utgarde Pinnacle, a level 80 dungeon.

The Nexus

Dungeons: The Nexus (71 - 73), The Oculus (80) – Raid: The Eye of Eternity (80)
Located in the Coldarra region of the Borean Tundra, The Nexus features two different 5-man wings - The Nexus intended for 70-72 and The Oculus for level 80 players. In addition, the Nexus features a 10/25-man raid at the The Eye of Eternity in which you battle the blue dragon Malygos (similar to pre-TBC's Onyxia raid)!

Azjol-Nerub

Dungeons: Azjol-Nerub (72 - 74) – Ahn'kahet (73 - 75)
The Nerubian kingdom of Azjol-Nerub will feature two 5-man instances filled with the spider-like nerubians and some of the most brilliantly detailed architecture seen in World of Warcraft. Azjol-Nerub is intended for players level 72-74 and Ahn'kahet "The Old Kingdom" is intended for players level 73-75.

Dungeon: Drak'Tharon Keep (74 - 76)

Located in Grizzly Hills, Drak'tharon Keep is the next step up for Wrath of the Lich King leveling instances, featuring a 5-man wing intended for level 74-76 players. The dungeon is filled with Scourge who have driven out the Ice Trolls.

Dungeon: The Violet Hold (75 - 77)

Dalaran, which formerly resided as a mysterious bubble out near the Alterac Mountains will be relocated to Northrend, where it will exist similar to Outland's Shattrath City and serve as a neutral city featuring a 5-man instance intended for level 75-77 players, The Violet Hold.

Dungeon: Gundrak (76 - 78)

Gundrak is located in the Ice Troll nation of Zul'Drak. The fierce Ice Trolls worship animal aspects which in turn assist them in battling the Scourge, and will serve as formidable enemies for even the most seasoned player.

Ulduar

Dungeons: Halls of Stone (77 - 79), Halls of Lightning (80) – Raid: Ulduar Raid (80)
Ulduar, located in the mountainous Storm Peaks, features three different instances - the Halls of Stone, a 5-man instance intended for 77-79 players, Halls of Lightning, a 5-man intended for level 80 players, and a currently unnamed Ulduar Raid zone, which will serve as the next step up from the newly relocated Naxxramas.

Dungeon: Stratholme Past (80)

The Caverns of Time out in Tanaris is being revisited, as well, with the addition of the Stratholme Past level 80 5-man. Here you will fight alongside Prince Arthas against Mal'Ganis, purging the (now-decimated) city of Stratholme which has been infected by the plague (just like in the Warcraft III: Reign of Chaos mission 'The Culling').