Cats scratch for several reasons. Don't believe the myth about sharpening their claws. They're actually removing old claw sheaths, exercising their muscles, and leaving markings from the scent glands in their paws. This natural behavior is frustrating if your feline friend does it on your good furniture, but it's not hard to redirect the scratching instinct to an appropriate place. Scratching posts come in a variety of styles and materials. You can likely find something suitable for your pet made from the three most popular materials. Combine this with other management techniques and your furniture will be spared
Carpeted scratching posts are the original standard. Some are covered in textured carpet, while others are made from berber. If you shop around enough, you can usually find a post in colors that match your furnishings, and I've seen crazy patterns like leopard spots and tiger stripes, too.
In the past I've owned cats who love carpeted posts, although it always made me nervous that they might switch over to the floor. Many felines have a preference for a particular carpet type, so it takes some experimentation to find the right scratching post.
One interesting innovation in this area is the ClawSkinz Eco-Friendly Scratching Post. This carpeted post is a green option because it comes with a removable tube of carpeting. You simply flip it over when your cat has scratched up the top. When both ends are all used up, dispose of the carpet and keep the base, simply replacing the scratching material with a new tube.
Most sisal scratching posts are wrapped in rope, like the Whisker City Sisal Kitty Cactus Scratching Post, although some are made from sisal material. My cats all prefer sisal posts, and I purchased flat sisal material pads to put near my area rug, where I noticed one of the cats scratching. He quickly changed his preference to the pads. Sisal is firmer than carpet and lets felines get a good "pull" as they groom their nails. Although I usually replace shredded sisal posts with new models, my husband occasionally rewraps destroyed posts with sisal rope he buys at the home improvement store. This is a good do-it-yourself project that saves you a few dollars.
I never thought of cardboard as a cat scratching post material until I purchased an elaborate cat tree that used it in one of its elements. Three of my cats ignored it, but the fourth absolutely loves it and has ripped several cardboard scratchers to shreds. Unlike carpeting, which usually requires you to replace the whole post when it gets destroyed, you can simply buy a refill for most cardboard scratchers. This replacement ability is useful, since cardboard doesn't last as long as other materials.
Many cardboard scratchers come in interesting shapes, like the Imperial Cat Scratch-N-Shapes.
My cats divide their time between scratching upright and stretching out on the floor to do it on their cardboard pads. They also like to lie on top of the pads, although I doubt they're officially meant to be cat beds.