The salesman from the tent in the Fields.
The salesman in the Lava Dungeon.
There is a salesman in the Lava Dungeon area and a salesman in the tent in the Fields. They each sell bundles of items, where the price on the bottom is what you pay for the package.
The fields salesman requires you to bring him sheep before he shows you his shop, and once you have done that he will sell you Logs, Feathers, Stardust, cooked chicken, bones, honey, Oak Logs, Dotted Green Leaf Seeds, small Stardust Potions, Cheese, Iron Dagger, Gold Leafs, and will sell you the unique achievement item, the Honey Tipped Stinger.
The Lava salesman requires you to fish him a lava eel before he shows you his shop. You can do that buy crafting a Lava Fishing Rod. Once you have done that, he can sell you Lava Logs, Lava, Fire Feathers, Stone, Ashes, raw eel and cooked Eel.