Do you mean the kind that sits in a window or one that's in the wall and stays there?

We had one at our old house that was in the wall and stayed there all the time. It did have the lattice around it painted the same color. It didn't show all that much and after a bit I don't remember noticing it unless I thought about it. Not very creative and will love to see what others come up with.

I have one that sits in the window here at the new house and changed the curtains to long lacy sheers to cover it from the inside and when on pull the sheer back out of the way.

Karyn

Not the window kind. Mine is a big, ugly thing that sits right beside the house, and smack in the middle of my garden.

How often do you need access to it for maintenance, etc.? Is it in sun? Shade? Not that I have any bright ideas at the moment, but maybe answering those questions will help inspire...

So far, we've never needed to access it, but at the same time, it does need to be accessible in case it ever does need maintenance. It's on the south side of the house and is in a pretty sunny location.

I made a bed around mine and planted some little leaf lilacs and spireas.
They are big enough to hide it now. But before they were I planted annual climbers (mostly wild cucumber) behind them that climbed up homemade little trellises.

I revamped the bed this spring and as you can see, I am not quite done laying the brick in yet. The meter is also hidden from the road.

Oh sorry, never thought about the ones on the ground. I have no suggestions, I have one of those submarine propane tanks I'm trying to hide. I'll keep my eyes on this one, there are great suggestions already.

Sassyrose I love those little trellises! Lilacs are a great idea, the bushes stay full even after they bloom. I love the sound of the leaves when the wind blows them.

Karyn

In the heating system, i remember about my floor radiant heating system (invisible heating system)!

I dressed up my home with a dual purpose fine art piece decorative air conditioner cover. The painting will cover any ductless air conditioner unit that measures less than or equal to 16" height X 31" width X 9" depth . The front panel to the painting can be opened to allow the AC/Heat to flow unobstructed. The painting is vented at the top to allow normal intake air flow. The front panel must be open to run the air conditioner. The link is
http://www.juliegudger.com/Incognito.html

Here is a link that might be useful: Decorative Air Conditioner Cover

Air Conditioner Cover will help prevent the elements (rain, mud, dust) from getting in when you are not using the unit.

Consider also that keeping the air conditioner in shade (with a free path to outgoing air) will make it more efficient too.

Plant some ornamental grasses around it. EASY to maintain, they're so pretty, but also allow easy access for maintenance people. Just cut them back to about six inches @ March and let them regrow each year.