This article is from the General Cat Care FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
There are various kinds of litter available.
* The traditional clay based litter is composed of clay particles that will absorb urine to some extent. In general, you need to scoop out solid matter regularly, and change the litter entirely once a week or so. Variations on clay particles include green pellets (resembling rabbit food) or shredded cedar (like hamster bedding). Examples include Tidy Cat, etc.
* There many varieties of cat litter that clump into little balls. This way, the urine can be scooped out along with the feces. In theory, you never need to change the litter again, you only add a little more to replace the loss to cleaning out the urine and feces (which offsets the initial cost). Sometimes the clumps break apart and there are some "extra strong" varieties to address this problem. The litter is usually sandy and tracks rather easily. Some cats seem to develop diarrhea with this litter; some people are rather allergic to the very fine dust from this type of litter. Currently, this appears to be the most popular type of cat litter, judging by what is available at pet supply stores. There is a non-sandy clumping litter called "Booda's Ultra Clump"; a drawback includes the clumps sticking to the pan itself (baking soda, pan liners, or small amounts of sandy clumping litter will remedy this). But it eliminates the tracking problems of the sandy kind of clumping litter. (It looks like regular clay-based litter.) There are now several brands similar to this. There exist some warnings about the safety of clumping litters. While some are extremely vague and unverifiable, such as the dust causing "immune system problems", one warning to take more seriously involves cats that ingest clumping litter. Since it swells into a solid mass, this can cause obstructions. Cats most at risk include kittens (who do not have to ingest very much to create a problem), and those who lick off large amounts of clumping litter from their paws or bodies. However, many cats have used clumping litter for years without problems, so whether clumping litter is a problem probably needs to be made on a case by case basis. Some references (all of these references are anecdotal and do not represent any serious studies of the potential problem):
* 4060 grade sandblasting grit made out of corncobs is an inexpensive alternative to clay-based clumping litter. It clumps as well as the flushable kind of clumping litter, and also smells better. It isn't available in all areas. In Ohio, The Anderson's General Store chain carries it for around US$10 for a 50 lb. bag, comparable to plain clay-based litter.
* Coarse corncob litter (commonly sold as "animal bedding and litter" by pet suppliers) about the size of peas, can be used. This is used in conjunction with a litter pan that has a screen and a drain pan underneath, into which the urine drains (and feces are removed as normal). It is almost completely dust free, unlike clay-based litters.
* "Good Mews." It is pelletized organic cellulose fiber ("scented with cedar oil--a natural flea and tick repellent"). It absorbs up to 1-1/2 its weight in water. According to reports, it is not dusty, sweeps up/cleans up easily, does not track, and does not cling to the tray when moist.
* There is at least one brand of litter that is intended for multiple cat households. This is Max Cat's Multi Cat, and it comes in both traditional clay and clumping forms.. Reports are that it pretty much works as advertised. Another way to control strong ammonia smells is to mix baking soda in with the litter.
* A litter called "PineFresh" is a natural pine wood litter that comes in little pellets. The pellets disintegrate in the urine and solid waste is scooped out. It's a bit expensive, plusses are described as: you don't have to change the litter as often provided the solid waste is cleaned out daily and the disintegrated stuff is sifted out twice a week. There is virtually no odor and no dust and it comes with a money back guarantee. It flushes just fine down non-septic systems. The product is manufactured by: Cansorb Industries 555 Kesler Road Cleveland, NC 27013.
* Plain sawdust or wood shavings can be used as litter. Some cats may not like it, since it doesn't absorb as well and may feel wet. But it is very cheap.
Some cats seem to prefer certain kinds of litter over others, you may need to experiment. A cat displeased with its litter box generally makes its feelings abundantly clear by finding a "better" litter box, such as your bed or sofa.