now that the limit is ten dungeons doubled from 5 here are the ones I think are worthwhile to farm.
going in order of level.
links don't belong to me just using so i can limit the guide to a few links and some suggestions
DUNGEONS
Zul'Farrak reason why.
How to Make Gold in WoW [5800 g in 23 minutes] Zul'Farrak Guide - YouTube
possible double gold per hour.
mageweave and transmog
best use of mageweave seen here.
Vision Dust Tailoring & Enchanting Shuffle - Silenthunder's WoW Gold Guides - YouTube
ZF is only good for classes that have speed increase, otherwise you'll waste 5-10m/run. The mobs dismount you so you'll have to walk. So stuff like druids and rogues are great for this.
The suffle is interesting, but you have to buy the recipe for the craft first. That's a 1.5k gold investement to start off with. Then on my high pop 4 mageweave =80s-1g+vendor mats (im guessing 10-20s) and the dust sells for 1g50s so 1item=2dusts=3g minus 1g costs, so 2g profit. Now you'd need to sell 750 dust to start making even with the inital recipe cost. Worth it only in the very long run or if the dust sells for more on your server. (there's some extra income from other d/e mats)
Stratholme for baron rivendares mount.
How to: Get Baron Rivendare Mount - Death Charger! - YouTube
noticable drops are runecloth
No real economical benefit? Good for mount farmers I guess
Magisters' Terrace non-heroic for phoenix hatching and blood elf costume.
WoW Gold - (5000g/hr) Magister's Terrace Gold Farming - Dubisttot - YouTube
possible double gold per hour
Hatchling sells for peanuts. 90g on my server. BC greens sell pretty badly because so easy to mass farm and useless for leveling purposes.
Halls of lightning non heroic.
WoW Gold - (12,500g/hr) Halls of Lightning Gold Farming - Tons of Gold Fast - Dubisttot - YouTube
guide seen here
Outright lie about the gph. Wotlk greens sell for nothing, the blues sell for nothing. There might be a tiny amount of exceptions. I've done this and at most I'd be getting 2k per hour if I get my junk to sell to clueless players who buy 77 items and don't know about cata greens.
Heroic Pit of saron trash runs for battered hilt.
Best instance by far to farm frostweave. I don't know how people gt stuck on the naxx farm. Naxx is like 500 cloth/hour last time I checked (2 weeks ago). PoS is 750+ or 10 runs (=less than 1 hour so would be 1000 cloth/hour), much faster and chance at 7k gold+ hilt. Two birds with one stone with more cloth and greens. Also easy rep farm if needed. 2m30s/run don't even have to spent an hour farming because you'll hit the 10 limit
And my toon has the increases cloth rate.
The Vortex Pinnacle for drake of the northwind.
use potion of treasure finding for extra gold per hour.
The stonecore for Vitreous Stone Drake
use potion of treasure finding for extra gold per hour.
Mounts, no real money profit.
RAIDS
Icecrown Citadel : The Plagueworks trash
stop before the bosses and clear the two dogs for 40 borean leather 20 each dog.
for a total of 400 borean leather an hour.
other notable drops are precious' ribbon
Interesting, never had a skinner that high, should try this. 1g+/each meaning 400g/hour if you include drops I guess you'd be around 1.5k gph so maybe not that great for gph...
Naxxramas
reason frostweave.
seen here
AMAZING Frostweave Cloth Farming Spot (Patch 5.4.8+) - 5K+ GOLD PER HOUR - YouTube
Overrated, see PoS
firelands trash for BOEs
BoT first room of trash
You need a really high ilvl for this 550+ and certain classes have a much easier time. Works great once you can do it tho.
credit where credit is to for all of these links
feel add to the list in comments

!