There is an abandoned shack near along the river between whiterun and winterhelm. Also an alchemists shack near riverwood. has an owner though who you would have to kill

Anywhere outside of your person or homes can be looted by npc's

If you're on the pc just dump your junk all over the ground. In my 50+ hours anything I ever dropped anywhere is still there. <_<

Because it was junk

I haven't personally seen it in the game, but on one of the gameplay videos pre-release where Todd Howard was doing a talkthrough, NPCs might take a fancy to some of the items you've dropped and pick them up.

The chest in front of High Hrothgar doesn't respawn if I remember correctly

That's the chest I use to store my stuff before getting a house.

Pretty sure it doesn't, those supplies have been in there for about 50 real life hours and i know dungeons have respawned in my game numerous times so it must be safe.

I was doing some science (read: Dropping objects of differing weight on NPCs from high in the air to see if they died or not, sadly they don't) and some dude walked off with a piece of dragon armor that I'd dropped on the person below me. So yes NPCs will walk off with your stuff if they think it is good enough.

Sometimes they actually ask if they can take the items (+1 beth).

Anyway, Labyrinthian bro, labyrinthian.

I tested this AI feature with a silver necklace. A near by merchant left his stand and asked me if he could have it. I was so hoping to see two NPC's fight it out.

I brought a few kettles to the Western Watchtower outside of Whiterun, placed them, and filled them with belongings I wanted but took up space otherwise. I've thoroughly decorated that tower and nothing has disappeared yet. It makes me feel like a renegade.
I've bought three houses, and I don't use them. :S

yes, actually; ever been to Mixwater Mill? there is a wood mill there with a signle lady that works the mill. if you go and spak to her she will tell you that she used to have workers helping run the mill before the war started but then they left when the war broke out and there is a little seemingly abandoned workers quarter near the mill that may interest you

if you've never been there, here are directions (use your paper map)
-head east along the white river near whiterun and head north when you come to the darkwater river and you'll come across the Mixwater Mill

DO NOT use dead dragons! There bodies/bones reset after 1 in game month IIRC.

ABANDONED SHACK... do the Dark Brotherhood beginning and you'll get your private house abandoned shack...

If the Mage College is safe for RP purposes, they give you a room with storage. I stopped using it, but I left a few items behind to test it out and they still haven't reset.

I've suspected this but it was generally my belief that named dragons never despawn while unnamed dragons will eventually fade away.

Exactly. The one at the Mage's College literally vanished.