The Post Office is a building which has been available in FarmVille since January 15th, 2010. It can be bought for 100,000 coins from the market, and bought gives the farmer 1,000 experience. It can also be obtained through Rhode Island Red Mystery Eggs. The Post Office serves no purpose; it is simply for decoration.
The Post Office can be created in the Craftshop by crafting the below Bushel combination over a 12 hour period:
4x Apple Wood Baskets
10x Cove Cranberry Bushels
6x Cauliflower Bushels