cimbrog
Explorer
If you'd like to focus a bit more on the merchanting aspect, and how to make an adventure out of it, I've found that the old Darokin Gazateer (GAZ11) is very useful for the merchanting (and caravaning) campaign I'm running right now. Cutthroat competitors for political-type adventures, quests and unexpected dangers for rare items to sell (like the high quality statues in the marketplace being sold by the medusa) and the thrill of fat profits. (Seriously, my group was more thrilled at the 280% profit they made hauling an eight headed hydra across the Broken Lands than the dragon hoard they found later.)