Conventional Litter 

• Simple kitty litter. Uses clay  to absorb moisture.
• Usually less expensive.
• Does not clump. This means you can easily scoop  out feces still, but urine will be nearly impossible to scoop.

Clumping Litter 

• The majority of the cat litter market.
• Easy to scoop out feces and urine.
• Usually only slightly more expensive than conventional litter.
• Some claim that the litter can be dangerous if ingested by cats, particularly kittens. There is not, however, significant scientific evidence to support this claim.

Biodegradable Litter 

• Litter is composed of pellets made from renewable plant  resources.
• Safe for flushing.
• Minimizes harm done to the environment.
• Good odor reducer. 
• Reduced "dust" characteristic makes it great for asthmatic cats and humans.
• Usually one of the more expensive litter options.

Silica Gel Litter 

• Has the best absorbency and odor control abilities, by far.
• Must stir daily after scooping, or urine may migrate to the bottom of the box and create a "pool" of sorts.
• Extremely light weight.
• More expensive than conventional litter.

Litter for Dogs 

• If you litter box train your dog, some manufacturers, such as Purina,  have created litter made specifically for dogs.
• Most biodegradable litter is good for dogs as well as cats.