I mean, I get my house looking just like I want it, with my Dragon Claw Collection all laid out, Dragon Priest masks all lined up on a shelf, etc...and then when I come back everything is scattered around on the dang floor, in the fire pit, etc.

This is ridiculous! The worthless baskets I drop around the streets of Whiterun are still there 50 levels later, exactly where I left them, but I can't leave my house for 10 minutes without coming back to complete disarray!

It will be fixed eventually, either by mods of by the devs. But if you think about it, it's not exactly a priority.

I only have one thing in my house: a statue of Dibella. I placed it on the table and my Poltergeist kept throwing it on the floor.

So I placed it on the floor on the rightside.

For some reason my Poltergeist likes it there and leaves it alone.

But you`re right.

I agree. Home decorating was one of my fav pastimes in Oblivion. The havok is horrible too. At least in Oblivion objects would commonly orient into "bottom-heavy" position. Not so in Skyrim. I cannot wait for this to be fixed/modded.

I think what happens is, when the house instances itself, objects are instanced first, then the shelves, cupboards, etc are instanced...so anything that was placed on a shelf that wasn't pre-coded to be there falls, and winds up on the floor somewhere.

They need to give us an armor display stand, where when you activate it, everything you're wearing (including weapons, armor, jewelry, etc) is all transferred to the stand, effectively "Dressing" it like you were dressed when you activated it.

It could be implemented like an invisible follower over a bare "frame" that takes what you're wearing and just equips it for display purposes.

Check the changelog of the 1.4 patch, I think Bethesda said something about fixing the issues you mention.
Personally, it isn't a big problem for me since I didn't purchase a house yet.
Edit: unfortunately Bethesda will only fix the problem with the bookshelves.

Huh. I don't suffer so much from it. The things I put somewhere mostly stay there, as long as it's put on a) a default empty space (on a table or something), or if I took the things that stood on that spot by default and threw them out of my house (if I leave them in the house, they'll have knocked the newly placed things out of the way when trying to put themselves there once again)

Well, sometimes something does change places, but it's not like all the decorations decided to have a party and suddenly remembered they have to act lifeless when you come home.

Quick fix:
Dropping items in your owned home, then simply exit and re-enter will (more often than not) cause them to stay where ever you then chose to place them.

^A lot of logic here and how I think the engine works as well. Hence the weird "whish" sound everytime you enter. But if you drop an item lets say on the floor and then re enter I think it will tag that object to be in there, and as long as you just move the object into place without putting it back in your inventory you can get it to stick most of the time. It's how I decorate my house.....granted though, the problem can pop up every once in a while to an object in the house. Im eagerly awaiting a decorating aide from the modders like they had in oblivion. You were able to lock objects in place, and I sorely miss that.

I like the 'insta dress' idea, saves a bit of menu navigating I guess.

Try this.

Drop any items you want to place on the floor. Go outside. quicksave and quickload. Go back inside and place your dropped items where you want them.