First off, if your dog is incontinent, make sure to get her a vet check with a urine analysis and if possible have them ultrasound.examine the kidneys, as one of the most common causes of death for dogs is kidney failure. Hopefully your dog is just old and leaky (LOL), but if the urine is dark or has a strong odor, be concerned.
When my dog was incontinent, we made an area for her to be in using a wire pen. We lined it with a large sheet of vinyl linoleum, then placed the pen on top. On top of this we layered pee pads (Wal Mart has large cheap ones, work fine.) The dog bed had a removable liner in it, we covered the filler cushion with a trash bag (contractor grade) and covered that with the washable liner. We had several of the same liner covers. If your dog is small enough, you can get water resistant dust mite pillow liners from wal mart and use those to cover a cheap pillow, they make great dog beds for small dogs. If your dog is large, consider buying a $30 waterproof baby mattress from Wal Mart and use blankets and sheets to cover it which you can wash. A great product you can put in the car, on the ground, dog bed, etc. is a product called "pooch pads", they come in a lot of different sizes and they suck up the urine and trap it so the dog isn't soaked in it (we used it as a top sheet on the dog bed, and in the car for vet trips), and it's machine washable and lasts many years. Buy two and you always have a clean one ready to go.
http://store.poochpad.com/poochpads.html
Another good product are the re-usable doggy diapers which you put an absorbant pee pad in - don't use the flimsy liners they sell to go with them, use poise pads for people, they work better.
