There are some wonderful farmers markets in Hawaii, but the Hilo Farmers Market is often cited as the best of the bunch. It's a great place to get an overview of the local bounty. The fruits and vegetables for sale are locally-grown, as are the herbs and nuts. There are also vendors selling jams and baked items made with local produce, as well as people selling excellent souvenirs – clothing, jewelry, and other handcrafted goods.
The market is open daily, but to get the full effect go on either Wednesday or Sunday when all the vendors are out. Even if you don't have a kitchen, a stroll through the Hilo Farmers Market is the perfect way to find out what's in season so you know what's fresh on menus.