Now we all know it can be difficult to remove that cat pee odor, especially from chairs and couches… Usually the best approach when dealing with cat pee is to use commercial products, safest for your carpets and the most effective. Sometimes though this can be avoided. Before you buy pet supplies online to deal with the cat pee removal why not try this free recipe I found on the internet.
(SOURCE: http://www.catsofaustralia.com/urinestainremoval.htm )

1. If the cat has recently urinated on the carpet, first absorb as much of the cat urine as possible using paper towels or an old towel. Place clean paper towels over the cat urine area and tread on them so as to absorb as much of the urine as possible. Repeat with dry towels until no more moisture can be absorbed.If the cat urine has dried and you are not sure where the soiled area is you can use a black light (pictured above) to detect it. In a darkened room the black light will pick up urine and other stains. Hand held black lights can be purchased for between $15 to $25
2. Next, wet the area with a solution of 50% white vinegar and 50% water. Make sure you use enough of the solution to penetrate the fibers deep down. Allow it to almost dry. You can assist drying by blotting with paper towels as described above. If you own a wet and dry vacuum extractor use that to remove excess moisture.The acidity of the vinegar will neutralize the ammonia in the cat urine.
3. Apply a liberal amount of baking soda over the affected area and drizzle it with a quarter of a cup of hydrogen peroxide mixed with a teaspoon of liquid dishwashing detergent. (not caustic detergent that you put in a dishwasher) Work it in with a scrubbing brush or your fingers (be sure to wear rubber gloves) to dissolve the baking soda and work it down into the carpet. Allow it to dry. Then vacuum.The vinegar will neutralize the ammonia and hydrogen peroxide is a powerful oxidizer capable of killing bacteria which cause the urine smells. Baking soda is a well known deodorizer which absorbs odors. Sprinkle it on your carpet monthly then vacuum up to keep your carpet smelling fresh all the time.

Important. Never use ammonia or ammonia-based products on the carpet. One of the ingredients of urine is ammonia and your cat may well be encouraged to re-offend in the same area if it detects the smell of ammonia. Many household cleaner cleaners contain ammonia so be sure to read the label.