Hi Apryl,
You can use any cat litter that is not clumping and is made from organic material. So this includes Feline Pine, Cat Country, Yesterday’s News. Corn cob litter is not supposed to be good for bunnies as it can cause digestive problems if they eat it. Pine shaving bedding is bad for bunnies too, it can cause respiratory problems, so try to stay away from pine unless it is pelleted. A good choice if you are looking for a cheap alternative is wood stove pellets or barn floor litter made from compressed saw dust. The wood stove pellets must be 100% wood, with no accelerants or other hydrocarbons added. The package should say 100% wood. The stove pellets can be found in hardware stores, usually as the weather cools. The barn stall litters are usually found in either feed stores for horses or places like Tractor Supply. I use something called “Barn Dry”, but I think there are many brands to choose from.