There are sprays available and devices that emit a sonic wave that upsets them

 

For cheap remedies (I have a lot of stray cats in my yard)....

a) Get a large container of peppercorns from the supermarket, and sprinkle a perimeter around your yard. Lasts about 2-4 weeks.

b)Get a gallon of Chlorox bleach, and pour a perimeter around your yard. Lasts a month if there is no rain.

Both are great repellants.