Try search, its been covered several times.
Here are a few, get Ingri and assess prices as the best destinations for commodities will change depending on how frequently you trade.
Akkerman - Salt
Kyzykerman - Leather
Bakhchisaray - Pottery
Cherkassk - Iron, Dye
Azaq-Kale - Powder
Sich - Dye, Powder
Kiev - Butter
Chernigov - Shag
Krakov - Tools
Warsaw - Beer