Any good ideas what to do with used kitty litter. the clumping kind.

Use the kitty litter to fill any gaps along your fence line, or depressions in your yard. You certainly can add it to a composting heap. Check with your city to see if you can add it to bagged refuge like raked leaves. If you have to dump it in the trash can, put it in a plastic shopping bag or a gallon size sealable storage bag. I think it is too acrid to use as potting soil or filler. I hope this helps.

Cat litter (any kind) that has any potty materials works great to get rid of moles. Just pour it in the top of the tunnels and the little pests go elsewhere.

You don't indicate what sort of litter you have. The clay based litter is pretty much impossible to use anywhere else. I recommend you switch to a grain based litter. There are many on the market, but I use chicken feed, Lay Crumble, it's essentially ground corn, same consistency as cat litter, and is completely biodegradable.

After removing the clumps, I use mine outside as compost. Another bonus, if the cat accidentally ingests it, it's not harmful to them. And, it's far less expensive than conventional litter.

Donate it to local animal shelter.

animal shelters are NOT going to want USED cat litter!

USED cat litter should be taken/sent to your local land fill; there is no sanitary method of 'composting' the clay base litters; Wood pellets, or grain base will eventually compost, but may attract feral or stray cats.

Feed stores for farm animals. I am in Southern CA and I get it for $14 for fifty pounds. I have seen it as low as $8 for fifty pounds. Just make sure it's Lay Crumble, which is same consistency as litter, and not Mash, which is too fine. There is also one size up, not sure what it's called, that's like tiny bird seed. You don't want that kind, either. Crumble denotes the grind.

Another bonus, as its lighter than clay, you get more volume, so you use less in the litter box.

Use it in your garden to repel rabbits.