[Butz]

Another idea, though much less secure than the playerhouses, are the bury bags. These can be made in Hirathia, and they allow you to store items inside of them.
When dropped on the ground, they become buried. You can later dig them up with a shovel by digging in the area where it was buried.
You would do well to pick a spot that isn't frequented by digging people. Areas that are bad ideas to bury include towns, map entrance areas, and around lumber mills.
To help you remember where you left your bag, you can create a marker on your map.
Press 'M' to bring up the map of the island, and drag one of the markers one the side over to the spot on the map where you left the bag. Use the /setmarker command to name it something.
Ex: /setmarker My Stash
Be warned though, that even if you bury away from common areas, if someone else comes by and digs in that spot, they can find it, so be sure not to store your extremely valuable items in this manner.
Good luck!