Once you have a high enough level character, head to Winterspring for a heap of great potential spots to Farm your Gold.
1. Lake Kel'Theril (53,42) is a frozen lake in central Winterspring. The shores of the lake are home to the Ruins of Kel'Theril, which along with the lake itself is populated by many tormented spirits of the Highborne. These souls are level 54 and 55 ghosts which are relateively weak, drop up to 8 silver and also have a chance of dropping green items and if you are lucky the odd epic item. For additional fun chests also spawn (randomly?) In this area, and every week the entire lake is invaded by water elementals commanded by Princess Tempestria. You can do quite well out of just killing the elementals and selling their 'Essense of Water' drops, but if you are up to it (group recommended) kill the princess herself and help yourself to the blue items she tends to drop. The invasion lasts until the princess is killed.
Heading South East from the lake to (57,50) you will find a whole heap of Cobalt dragons (56-58 elites) around a cave. Killing the little dragons (Wyrmkins, scalebanes and mageweavers) has a small chance of dropping a 'Mature Blue Dragon Sinew'. This you sell to the highest bidder – and believe me they will bid as it is a very hard to get item and is required for a high level Hunter quest.
2. Everlook is a trading post run by the goblins of the Steamwheedle Cartel. It lies at the crossroads of Winterspring's main trade routes. Head North and East to (67,40) and you'll find an excellent area to farm Ice Thistle Yetis. As well as dropping vendor trash items, and sometimes blue items, you can also skin them for rugged and thick leather which sells consistently well.
3. Darkwhisper Gorge.
Aside from bashing Frostmaul guys who have about a 1/50 chance of dropping a 'Greater Frost Protection Potion Recipe', you can travel on down to (60,75) and try your luck against some level 60 elite demons (Grouping is STRONGLY recommended ). You'll get a heap of Felcloth and Runecloth drops, as well as Green items. There's about a 1 in 50 chance of getting 'Eye of Shadow' which can sell for several hundred gold coins.
Between these three locations you should be rolling in gold in no time!