Here is a list of items you can use to stop a cat from scratching:
A bottle/can with something noisy in it
Air (I use a balloon pump)
Aluminum foil
Anything citrus smelling (spray/rub in on whatever they’re starching)
Double sided tape
Dumb Cat Anti-Marking & Cat Spray Remover (Spray-Petco-This one is for urine)
Four Paws Cat and Kitten Repellent (Spray-Petco)
Four Paws Keep Off Indoor and Outdoor Dog and Cat Repellent (Spray-Petco)
Fresh Kitty Furniture Protectors
Gingerroot
Packaging tape
Pet Botanics Bitter End Training Aid (Spray-Petco)
Pet Organics No Scratch! for Cats (Spray-Petco)
Pet Organics No-Mark for Cats (Spray-Petco-This one is for urine)
Pet Organics No-Stay Furniture Spray for Cats (Spray-Petsmart)
Scratching post
Simple Solution Indoor/Outdoor Repellent for Dogs and Cats (Spray-Petco)
Softpaws
Spray that stops them (there all different kinds)
Spray that stops them (there all different kinds-just go to petco.com type in “scratch spray”)
Trim their nails back once a week
Water bottle spray

Also if you have a scratching post & your cat is not using it you can get some catnip & rub it on there or they sell catnip spray. Also it might not be big enough. A scratching post needs to be as tall as that cat (about 32”).

Here is a little info of declawing:
Onychectomy (Declawing)
You should read these websites. To see what declawing really is. It’s not a simple surgery of removing the “claw”. It’s an amputation of 10 digits.

Please do not get your cat declawed. Most of the problems with declawing has nothing to do with the actual surgery. Declawing is the worst thing you could ever do for your cat-other than not getting I fixed. Most cats that do have problems are not visible. Most of it has to do with their back muscles. Cats need their claws in order to stretch properly. That would be like a human not being able to stretch when they wake up in the morning. Imagine how stiff you would be. That results in back problems their whole life. And because cats are VERY good at hiding pain/sickness you can’t really tell.

Also you should know that when a veterinarian declaws a cat without trying everything else possible they are breaking the AVMA (American Veterinary Medical Association) guidelines: Declawing of domestic cats should be considered only after attempts have been made to prevent the cat from using its claws destructively or when its clawing presents a zoonotic risk for its owner(s).

Also people think it’s better if they get it done laser. NOT TRUE. Watch this video. It’s long, but worth it. The part about laser is 10:44 into the video
http://www.youtube.com/watch?v=KaEx-qe2wBw

All of the stuff below is from research & the websites listed below. Not written by me.
A few quick facts:
The Cat’s Claws:
Unlike most mammals who walk on the soles of the paws or feet, cats are digitigrade, which means they walk on their toes. Their back, shoulder, paw & leg joints, muscles, tendons, ligaments & nerves are naturally designed to support & distribute the cat’s weight across its toes as it walks, runs & climbs. The claws are used for balance, exercising & stretching the muscles in their legs, back, shoulders & paws. They stretch these muscles by digging their claws into a surface & pulling back against their own clawhold-similar to isometric exercising for humans. This is the only way a cat can exercise, stretch & tone the muscles of its back & shoulders. The toes help the foot meet the ground at a precise angle to keep the leg, shoulder & back muscles & joints in proper alignment. Removal of the last digits of the toes drastically alters the conformation of their feet & causes the feet to meet the ground at an unnatural angle that can cause back pain similar to that in humans caused by wearing improper shoes.

The cat’s claw is not a nail as is a human fingernail, it is part of the last bone in the cat’s toe.

Declawing is not a “simple”, single surgery but 10 separate, painful amputations of the third phalanx up to the last joint of each toe.

"Declawing is actually an amputation of the last joint of your cat’s "toes". – Christianne Schelling, DVM.

“Fifty percent of the cats had one or more complications immediately after surgery…. 19.8% developed complications after release.”

Many vets deliberately misinform & mislead clients into believing that declawing removes only the claws.

Many cats also suffer a loss of balance because they can no longer achieve a secure foothold on their amputated stumps.

"Among 218 cats relinquished to a shelter, more (52.4%) declawed cats than non-declawed cats (29.1%) were reported by owners to have inappropriate elimination problems."

Psychological & Behavioral Complications:
Cats who were lively & friendly become withdrawn & introverted after being declawed.

In some cases, when declawed cats use the litterbox after surgery, their feet are so tender they associate their new pain with the box…permanently, resulting in a life-long adversion to using the litter box.

Other declawed cats that can no longer mark with their claws, they mark with urine.

Others, deprived of their primary means of defense, become nervous, fearful, and/or aggressive, often resorting to their only remaining means of defense, their teeth.

Many declawed cats become so traumatized by this painful mutilation that they end up spending their maladjusted lives perched on top of doors & refrigerators, out of reach of real & imaginary predators against whom they no longer have any adequate defense.

Unlike routine recoveries, including recovery from neutering surgeries, which are fairly peaceful, declawing surgery results in cats bouncing off the walls of the recovery cage because of excruciating pain.

A declawed cat frequently resorts to biting when confronted with even minor threats. Balance is affected by the inability to grasp with their claws.

Removing the claws makes a cat feel defenseless. The constant state of stress caused by a feeling of defenselessness may make some declawed cats more prone to disease. Stress leads to a myriad of physical & psychological disorders including supression of the immune system, cystitis & irritable bowel syndrome

Some veterinarians are now promoting laser declawing as a "guilt-free" procedure. While laser declawing can reduce the bleeding & perhaps diminish, to some extent, the agonizing pain, the procedure is the no different, only the means of amputation.

A cat relies on its claws as its primary means of defense. Removing the claws makes a cat feel defenseless. The constant state of stress caused by a feeling of defenselessness may make some declawed cats more prone to disease. Stress leads to a myriad of physical and psychological disorders including supression of the immune system, cystitis and irritable bowel syndrome.