Been looking for these as much as I can. Here's my current list:
1. Borean Tundra - Steam Clouds in the Gyser Fields.
2. Northern Howling Fjord - Artic Clouds in the snow areas.
3. Dragonblight - Frozen Spheres in the north area where the harpies are. Have reports of "fire" clouds in the Obsidian Dragonshire also.
Please feel free to add to this list... I have hopes we will see other cloud types soon... I have high hopes of finding a shadow cloud.
In sholazar there's cinder clouds around the dragon area in the north west, there's also steam clouds floating around.
In icecrown and storm peaks there's arctic clouds. I've found them all over the map, not sure if there's a particular area where they stay.
There are 2 cinder clouds floating around the fire elemental area of Wintergrasp. (and in that area is a sort of ledge where the zone changes to Dragonblight so it's possible to fly away from there if you don't fancy being ganked by anyone farming the fire ele's).
There is also 1 cinder cloud I know of that floats around the black dragon shrine in Dragonblight.
Cinder clouds tend to give me about 2-4 crystallised fire depending on when they were last harvested.
From what I've seen, it doesn't matter WHEN they were harvested, seems to be a random amount.
I can confirm this. I was questing last night in Dragonblight and on the way into a cave I received 2 crystalized fire then on the way out after doing a few quests the node respawned and I received 4 crystalized fire.
Steam Clouds = Low Air / High Fire (like 1 Crystallized Air and 3 Crystallized Fire)
Cinder Clouds = 2-4 Crystalized Fire
Artic Clouds = 2-4 Air OR Water... but never both at the same time
I took time out last night and went for long tour of northrend (at least I got my explorer achievement). I found that Storm Peaks, Ice Crown and Dragonblight have many artic clouds in what would seem to be many random locations (I found one up on the north shelf by the cliffs in icecrown and one on the side of the high peak for the Temple of Storms). It did not matter if you were near water or ice... the locations are everywhere.
Steam Clouds are prevalent in Sholazar Basin (repeated extracts near Rainspeaker Rapids) and Borean Tundra (Gyser Fields).
Cinder Clouds were found in Sholazar Basin, Dragonblight and Wintergrasp. Only one cloud was found in the Basin (The Savage Thicket) and it seemed to have a very slow respawn. Dragonblight produced a cloud in the Obsidian Dragonshine. Just above the dragonshine to the southwest there is an elevated lavafield (safe to walk) that's eastern boder is still in Dragonblight. However, the field itself is in Wintergrasp. I'd land up on this ledge first and survey the area to make sure farming the 2 cinder clouds up here is in your best interstes.
On this tour of northrend last night I managed to pull in about 40 Crystallized Fire, 29 Air, 18 Water.
I'm bummed that Shadow is not available, and I have yet to see a Crystallized Mana show up anywhere... but I believe that is being removed as Alchemy: Transmute Eternal Might does not have a mana type requirement.
Is seems we are no longer able to gather 4 types of elements (Mana,Shadow,Water,Air) but now we can only collect 3 (Fire,Water,Air). The only flip-side to collecting less types is that less types are available also (4/6 BC to 3/5 wotlk - roughly 6% less effective). Lets hope the addition of our massive fire gathering skills pays off...
So farming the gas clouds can be done with the same device from Outlands made by engineers?
Not only can you use the Zapthrottle Mote Extractor, but all helms which tracked clouds in BC will track the new clouds in Northrend. There is also a new tinkering item that can be attached to any belt called Belt-Clipped Spynoculars that will allow far sight and Cloud Tracking also.