I was trying to find a listing of plants that cats don't like... and found this website with helpful suggestions, the main one being, cats don't like petunias. Who knew?
Garden Helper Tips
Here's some advice from another website:
Sticky surfaces: One way to deter behavior is to put down a surface that cats don't like to walk on. Wallpaper (sticky side up) or double-side tape works well. Once they jump on that sticky surface they are not likely to try it again.
(Oh just think of the opportunities to laugh...)
Prickly surfaces: Put down a plastic carpet runner, pointy side up, and your cat will be unlikely to return to this area again.
(this might be pretty good for a laugh, too!)
Unpleasant smells: Cats can be repelled by certain smells. IF there is an area you don't want your cat trafficking, use one of the following:
Citrus juice
Cologne
Muscle rub (such as Ben-Gay)
Aloe gel
Bitter apple