From Jim W. in New Jersey...
In regard to gopher holes, I read about this method in a garden web forum and it worked immediately for me. We poured used cat litter down the main gopher hole. Don't know why it worked but it did. We had tried filling in the hole several times and he just kept digging them up. Once we poured in the litter and filled in the hole, the gopher never returned.
Editors note: While I haven't put this method to the test, it's certainly worth a try before going to the expense and trouble of setting traps. Used litter obviously contains urine, which often contains certain pheromones used to mark their territory. Combined with the urine, these elements make for a pretty potent mix that isn't easily removed (ask anyone who owns a cat). A cat is also a natural predator of gophers. Now, whether it's the gophers basic survival instincts or the fact that gophers don't care much for the smell, it must send them packing to a safer more aromatic area, like your neighbors yard.
Thanks Jim for the advice.