I have a puppy who is 5 months months and I posted a thread about struggling to leave him on his own, as he would bark when I walked out the door.
I know its something that a lot of people are struggling with, so wanted to feedback that I've had some success with this, and can now leave him for an hour. (I haven't tried longer than this yet and don't really need to at the mo).
He isn't crate trained, and sleeps on a bed on the floor in our bedroom, so I was leaving him in the kitchen with the door shut when I went out. He didn't like this and barked a lot. I experimented and he seemed to be happier with access to more space, now he has the hall and 2 other rooms and just sleeps when I go out. (He has been to the loo/had food/exercise etc first). He doesn't bark.
I have a camera so can see what he is up to, and I leave the radio on.
He isn't much of a chewer (yet!) and so I can imagine this set up wouldn't work for every dog, although I've tried to make the environment as chew proof as possible.
I just wanted to reassure people who haven't tried it yet, that I was really despairing about ever leaving him, but by tweaking things I seem to have found a set-up that he finds relaxing. I also wonder if he was a bit more mature and settled when I started to leave him, who knows, other people's puppy's have been fine from day one!