Everyone knows that Un'Goro crater is a good spot for farming. Herbalists will find Mountain Silversage in abundance. There's one particular area that helped this Warlock gain the gold needed for his level 60 mount & that's Fire Plume Ridge.
Preparation
You need a hardy pet (Blueberry or FelGuard). Also ready your 30 & 15 second banish spells along with Curse of Doom. Bring lots of heavy bandages as you'll be here for a while and you'll not want to have to bow out early to re-supply.
Quarry
Climb up to the top of the ridge by the lava lake. There are Fire Elementals all over the place. What you want to do is double-up on kills. Drop a Curse of Doom on an Elemental then immediately banish it. Send your pet on a second Elemental & drop curses to take it down. No need to burn to hard here; conserve mana cuz this is a grind. After 30 seconds expires your banished Elemental will be freed up. Drop another 15 second banish on him. You want to time it so that your pets' Elemental goes down just as the second banish releases. Have your pet in position before it goes off if possible. Now, drain life / life tap to regenerate mana as you wait for the Curse of Doom to go off. 99% of the time the COD will drop the Elemental & you don't need to do any extra work. Rinse and repeat. The repop rate is high enough so that you can pretty much be killing MOBs non-stop even if there's someone else farming in the vicinity. Just be careful to conserve mana.
Rewards
These guys drop some vendor trash but the golden nuggets you're after are Heart of Fire. They seem to drop every 40-50 kills in this zone and can sometimes fetch up to 8G in the Auction House on my server. I've had occasions though where I grabbed 3 in a 45 minute span. These guys also drop elemental fire which can sell for good cash if you have a stack. It's components for Fire Protection potions. Always try to unload these items in the trade channel though before heading to the Auction House though; often people are looking for this item before heading off to Molten Core.