With the launch of Cataclysm, we will be able to enjoy 8 5-player dungeons and 2 special Heroic Dungeons for level 85, which will be Deathmines and Darkfang Castle (in Wrath of the Lich King there were originally 10). This article can also be found in the Cataclysm Guide.
Abyssal Maw
We can find 2 dungeons within the Abyssal Maw, one for level 81-83 and another for level 82-84. And we can find her in the submerged City of Vashj'ir, jumping into a vortex of water! Like the vast majority of Cataclysm dungeons, it will not be linear. It is known that it will be on the ocean floor and that there will be windows to look through to see the ocean taking advantage of new technology to render the water. It is just the place where one imagines the water elementals live. Aquatic creatures like elementals or even huge Krakens will abound. It is the home of Neptulon the Tide Hunter, lord of the water plane who fights incessantly against Ragnaros due to the proximity of the 2 elemental planes.
Skywall (Level 80-82)
Above the sun, the fortress of the Elementals of Air rises. With rock stolen from lower planes, there are walls supported by permanent cyclones. Strong winds and lightning strike the Elemental Plane of Air so flying there without some kind of magic would be completely impossible. Al'Akir, Lord of the Wind reign over this plane.
To inflate
Beneath Skywall is the area of Deepholm, the elemental plane ruled by Therazane, Mother Stone. Numerous earthquakes run through the area and the dungeon will be for levels 81-83.
Uldum
In Uldum we will find 2 Dungeons for 5 players. One for players of levels 84-85 and one for levels 85.
Chambers of Creation
From what could be seen of this dungeon, it has a strong Titanic component with Egyptian touches such as Pyramids and Hieroglyphics. Something lurks deep within this Chamber and is longed for by the Alliance, Horde, and the Cult of the Twilight's Hammer. It is believed to be a super secret weapon.
We can see Brann Bronzebeard there, as always hungry for titanic secrets.
The Lost City of Tol'vir
This huge, open-air dungeon is home to the Tol'vir, a new race that we will see in Cataclysm that was created by the Titans. They have the appearance of "stone cats" and it is known that we will face 7 bosses within it.
Blackrock Cavern (Level 85)
This new dungeon inspired by the previous ones in Blackrock Depths and Peaks, has new arts, new creatures and of course, new loot. We will see the Cult of the Twilight's Hammer now in service to Deathwing. You will have the opportunity to find out why they are there and what they want.
Grim Batol (Level 85)
Grim Batol is Deathwing's new home and is the place where the Flights used to store their eggs. Deathwing has created a new flight, Twilight. There is not great information about this dungeon but it is known that we will fight against 4 bosses.
Bands in Cataclysm
In addition there will be 4 bands of 10 and 25 players (originally, in Wrath of The Lich King, there were 3)
The descent of Blackwing
This raid, inspired by Blackwing Lair, we will be able to see Nefarian again with new creatures, loot and of course a completely new dungeon.
The Firelands
The Firelands are nothing other than the Elemental Plane of Fire. We will fight Ragnaros to his full potential in Sulfuron's stronghold as we will be fighting in his element.
Sky wall
The kingdom of Al'Akir will be another band, they have not commented anything on this band although we probably fight against Al'Akir himself, Lord of the wind.
Grim batol
Nothing has been said about the GrimBatol band but as we have already mentioned, it is the new place of Deathwing. I doubt that at the exit of Cataclysm we can fight Deathwing since he is the villain of the expansion and is supposed to be the final boss of it.