We already are getting visitors after just a short time since launch, particularly with questions on how to mount a flat screen in the corner and setup the mount.
It has been my experience that the 55″ LED TV is about as big as you want to go with an off the shelf articulating mount. BE WARNED the Chinese cut corners and the metal used in most of these mounts is garbage. The TV will Sag and the metal holding the mount to the wall starts to rip with time. Not only does your Mount need to hold your LED TV firmly to the wall it needs to support the weight and force you put on it when you swing the TV because you changed the furniture in the room or you need to get behind it for some reason. This is just not a place to cut corners when you are placing your LED TV in the Corner.

Full Range of motion of the Wall mount allows you to change the furniture around later without needing to remount the LED TV
I highly recommend the Sanus Systems VLF220 VisionMount Large Full Motion Wall Mount, this mount has more than enough articulation to safely mount a LED TV in the corner of a room safely. The arms are cast not stamped steel so they will never sag and the mounting of it fairly straight forward and it should only take a few hours if you check your math twice and hunt for studs in the wall properly. Now I sell these mounts from the store for $359 retail and they are worth every penny, but through our link someone is probably trying to wholesale one or two of them because they didn’t know how to sell or install a quality mount.
First when you picking a corner you will have some things to consider. How high can I go and have the TV clear properly, how far from the wall to make it fit in the corner and seem balanced.
To start try to pick an exterior wall, The studs in that wall will be better quality and more likely to be 16 inch on center where some interior walls have been 24 inch on center in recent years to save money. Also if your mounting a Sharp LED TV in a master bedroom that means there is a room that leads to the bathroom, that wall can have plumbing inside it if your shower is butted against the same wall on the other side so avoid that spot and use the exterior wall planning again.
Now a standard 55 inch LED TV is not 55 inches wide, if you bought a new full motion picture quality TV your usually between 50-52″ wide and only about 34-36″ tall. What you want to do is add 8″ to the Height of your TV so lets say 42″ by 52″ is our math. With the mount we suggested above all you really have to do is find the first stud that is more than 10 inches from the corner and it will usually be 14 to 18″ when measuring a painted and finished wall. Here is a solid tip if you don’t have a stud finder USE A MAGNET to find where the screws holding the sheet rock are. The magnet will center itself over screw and you best hope that the sheet rock guy didn’t cut any corners that you are dead over the stud.
Now from the ceiling we want to divide our TV height plus 8 inches by 2 so in our example (36 + 8)/2 = 22 inches This is where we want the CENTER of the mount to be at so that we have 4 inches of clearance for swing above TV. Also when you go to hang your TV you have to come in high and latch it in a downward fashion and you need room for this to take place. Also another pro tip is to LOCK THE ARMS BEFORE YOU HANG THE TV or you wind up chasing the mount to the wall as you hang it, you fall new TV breaks much laughter ensues, etc etc.
There are some adjustments on the back of the arm to lock out the wiggle and the ability for the TV to come OFF the mount. Use them.