Find a corpse with an item or souls, and grab the loot. Now make a fatal leap off the nearest ledge. As soon as you die, quickly press the appropriate button to bring up the option to quit your game. When you restart, you will be at the last bonfire with whatever you picked up from the body now located within your inventory. If you go find the body, the item should also be waiting on the body, allowing you to pick it up again and repeat the process as often as desired.