This is an old, unanswered thread, but I think this is a common problem and this is my solution:

A few years ago my neighbors got a boat and parked it in the back of their driveway - the side of my backyard. Now, it is illegal to have a boat that can be seen from the street, but it was in their backyard (their garage is at the back of their property and their driveway is on the border of my propery), and behind their back gate. So, I had to look at this monstrosity through my windows everyday until they put it in the water in May.

This is what I did:
I built a 30" high raised bed of 2x10's stacked 3 high and at the back I used 4x4 posts and made an 8' tall peaked lattice wall. I only made it 30" wide (big mistake) and angled it in the corner of my fence. It is not permanent - the posts are screwed inside the raised bed and the dirt holds it up. I have Sweet Peat vines growing up it and a Sky Pencil Holly planted in the center of the bed.

Because it is not wide it does not provide much privacy, but it definitely provides a pretty view and it does obscure my view of the neighbors. It is 10' high at the peak, 8' high at the sides, and the way it is angled it gives the most privacy from my neighbors when they are out on their back deck (you'd be surprised how a deck only one foot off the ground gives your neighbors a bird's eye view into your yard).

Well guess what? The year after I built my "wall" they sold their boat! So that they could turn their garage into a pool hall! Now, when they have people over they all hang out right next to my fence and stare into my garden! My fence is solid for 5' and lattice at the top - exactly where most people's heads are.

Now I am going to remove some of the Rose of Sharon's I have growing along the fence and build a giant 12 foot long lattice wall (in 3 parts).

And last year my neighbors directly behind me decided it was cheaper to store their boat at the back of their driveway too! Now I have a huge boat staring at me from my back door and master bedroom windows. I have big trees back there, so a structure will be more difficult. I'm thinking of building a tall potting shed.

We are not allowed to have a fence over 6' and you are supposed to get a permit for pergolas etc. But, my way around those rules is that it is not cemented into the ground. Technically it IS a raised bed!

Neighbors can be a pain sometimes. In another house, my neighbor had this huge tree that shaded one side of my yard most of the day, so I had a wonderful shade loving, garden there. They sold their house to an idiot who cut that tree down! Ruined my entire ecosystem!!

If you have any sun at all, grapes love sun, look pretty all summer, and they will grow as tall as you let them! I'd put in some poles, string some wire across, and let grapes grow there. While they are dormant, they won't block the view, but not too many folks sit on their decks in the snow!

You won't care anyway because you'll be drinking wine you made from all those grapes!