You can also trade in the F&H, Swamp, Jungle, and Desert area. Here's the more detailed locations:
Forest & Hills: Area 7
Jungle: Base Camp, top of the cliffs near the bee hive
Swamp: Base camp
Desert: Felyne's Den in Area 8
Now there's a Faq on the Elder Trades, and it gives specific details on what items you get for different items. One elder give you bones and monster material, another one gives you support items like immunizer's and stuff like that, and another elder will give you iron materials like iron ore and machalite ore.