A great item to go and do some WoW gold farming for is the Big Iron Fishing Pole. This item usually sells on the Auction House for around 32 gold.
In order to get this item head to the Shadowprey Village in Desolace. It is a Horde controlled village,so you Alliance that want to do this must be careful. Once you make it to the village (or near the village) head out into the water and head west. It is best to bring along a few Water Breathing Potions. Just west of the docks you will be a bunch of submerged cages scattered throughout the seabed. In order to find the Big Iron Fishing Pole you will need to open these cages. The cages will normally spawn a level 33-34 mob, but once in a while they drop the Big Iron Fishing Pole. I figure you could probably make a solid 3-4 gold and hour in this location with all of the other drops of vendor trash and possible green items.
This spot can be a tedious place to do some WoW gold farming if you play on a crowded server, but can be very rewarding if you give it a try.