I've had cats as long as I've had ferrets.  When my cats were younger they
played a lot w/ the ferrets.  My cats are older now and I now have younger
ferrets.  My ferrets love to tease and bite at the cats.  The cats take it
for a bit, or slap them back then run away.  The big thing is to make sure
the more submissive animal (ferret or cat) has somewhere to go away from
the other, the cats get on the bed or table or such and the ferrets can
run under the couch or go in their cage.  My dog play great w/ the ferrets
(one of my dogs weights less then my biggest ferret :) ).  I also foster
and raise orphan kittens, the best thing i have found when introducing
any new animal to my house is time and patients.  I make sure to give the
resident animals tons of extra attention and make sure everyone has their
own private space, this is a big help.
 
Good luck,
[Posted in FML issue 3685]