Many people use different oils/scents to deter a cat from a certain area of the house. We stuck a citrus scented air freshener inside the Christmas tree and the cat stopped climbing into it. This will not just keep the cat from scratching the furniture though, it will probably keep it from coming anywhere near the furniture as well. So if you like cuddling with fluffy on the sofa, then I would not recommend spraying it with orange perfume.

There is a whole list of scents that cats detest. So if you don't like the smell of oranges there may be an alternative that you do like.

Cats also will not walk on aluminum foil. This is helpful in keeping them from using potted plants as an extra litter box. Just place foil on top of the soil in the plant. After a while the cat will assume that it's still there and stay out of that plant (and other potted plants as well depending on the intelligence level of the cat).