In Dawnstar, just left of the entrance to Iron-Breaker Mine, are a tree and three rocks. Approach the rock in the back and look down at it and you will receive a prompt to open a chest. Do so and you will find large quantities of equipment (both enchanted and standard), gold, crafting consumables and potions. These items will improve in quality as your level increases. The chest is tied to the salable inventory of the Khajit Ahkari. Ahkari wanders Skyrim with her caravan, but can be easily found outside Dawnstar. If you Fast Travel to Dawnstar, she will be in the tent immediately behind you. If you do not see the group, Wait (by pressing Select and waiting in-game hours) until she is there.
There are two ways to respawn the chest. If you wait 48 in-game hours her inventory will restock, restocking the chest's contents as well. Alternately, you can save the game next to Ahkari, then kill her. Reload the save you just made and view her inventory. It will have restocked along with the chest's contents!