What kind of bedding is best?

Tom found wood shavings best as long as they are not dusty or only chips. Curly shavings don't pack down as much, and dry out better. Pine and cedar tends to cause resp. problems, but Tom claimed to have had a healthy five-year-old on cedar.
Aspen shavings are the best and are found by the name Sani-Chips at most feed stores and lab supply outfits. Newspaper bedding is not good for rats and colored inks can be toxic, so avoid newspapers. Corncob is okay, but not very absorbent or nice to sleep on. Corncob bedding also has a tendency to grow molds very quickly. There are also books which warn of corncob bedding causing "ringtail" in some rats. (ie. "Rats: a complete pets owner's manual" by Himsel published by Barron's;pp.21 & 58.)
Paper bedding (not newspaper) is fine for rats. Just make sure you use a good brand such as CareFRESH 1-800-242-2287 or Cellu-Dri. There are also several others. Sani-Chips are the best hardwood bedding available. Call the manufacturer, P.J. Murphy Forest Products at 1-800-631-1936 to see where you can get them in your area.
There is now both grass and straw pellets available. The straw pellets are sold under the name Critter Country and are highly recommended for reptiles as well as rodents, clump well and hold heat well in heated cages. They are the most expensive however.
Warning: Pine shavings have been known to carry red mites, cause liver and kidney damage, and respiratory disease. So can cedar. Also beware of feed stores that store their shavings of any kind next to live poultry, as I know more then one person who found mites in their shavings, but it was the fault of the feed store that the pigeon and chicken cages were right next to the stack of shaving bags.

Safe Pet Bedding FAQ