Regular Cat Litter - Never use it. Does nothing for odor and is extremely dusty. Far dustier than the clumping version. Not much more to say on it other than... don't use it! Clumping Cat Litter - I used this for many, many years without ill effect. I think different product manufacturers make a difference in what brand has a higher dust content. My ferrets snorkeled in it all the time with no after affects. Clumping litter is good to use if you are the type of person who wants to clean a litter box all the time. I find if you wait too long and you have a large number of ferrets, gunk is more the word I would use as to what comes out of the litter pan. It can get messy and it tracks everywhere. It does not rate high for odor control. Litter Pearls - yuck! The little pearls don't stay in the litter box and always seem to end up under my feet, and are they ever painful to step on! They seem to do the job of keeping odor down, and absorbing the urine. I didn't have much of a problem getting the poop out. Overall, I just found it inconvenient. The ferrets tracked it everywhere and it stuck to their feet. I haven't used it in months and yet I still keep finding little pearls everywhere! Sheesh! Yesterday's News - I find it does not keep the odor down as well as wood pellets. It is hard (and messy) to sift through. I find I waste a lot of it trying to get out the used and loose stuff. It is not as expensive as Litter Pearls, so if I had to choose between the two, I would pick Yesterday's News. Wood Pellets - My all time most favourite litter! Easy to clean the box... keeps odor almost down to nil... cheap like borscht... and convenient. Downside... not in control of what is the main ingredient. Recently, my supplier changed the "formula". I found the wood pellets is this shipment were smaller and broke up a lot easier than the "old formula". I can't recall what was in what, but even the color has changed. Sure, you might notice more particles on your carpet, and have more to vacuum up, but I have tile, and just sweep. My cats won't use it (too bad) and so I never have to worry about my ferrets not using a box because it was invaded by a non-ferret species. Wood pellets are my number one choice. Newspaper - Always on hand for those ferrets who are too old, or too sick to use a litter box. Makes a great back up in those spots that are targeted as high hitters for ferrets. It is cheap and everyone is willing to let you have all you can take. I can never seem to get enough of it. Downside is that the poor little guys get black feet from the ink. So, I use it only where I have to, and in compliment to Wood Pellets. Betty and Her Blur O'Fur [Posted in FML issue 3139]