What is a good cat repellant?

One way to keep cats out of your garden is the following: Every time you make a pot of coffee, set aside the used coffee grounds until they are dried out (you can continuously use a plastic container specifically for thisa purpose). One the used coffee grounds are dried out, take them out to your garden and spread/sprinkle them in and around the area where you don't want cats going. The extra benefit of this is that the used coffee grounds have certain nitrates in them that plants love and therefore they are a good fertilizer as well.