You can also stell your farm-fresh produce to your in-game friends; to do this, simply purchase a Marketplace in the first tab of your shop.
You can click on the market stall to sell goods (and leave a friendly message for visiting friends). Just click on a free slot to choose a product you would like to sell. You can determine how many you would like to sell, and how expensive you want your goods to be. Visiting friends will be able to view your market stall and buy what you have for sale.
In the tab with the shooting star, you can also let your friends know what you're looking to buy and at what price. If your friends are looking for certain products, you'll also be able to see what they want so that you can put that up for sale for them in the first tab!