There are countless possibilities here. Just a box by itself is fun for a
little while. Stuffing it with things is where you give ferrets the most to do.
Packing peanuts are a start. Their static electricity causes them to cling to
the ferret's fur. They go nuts trying to get the peanuts off, clucking happily
the entire time. Dry fall leaves, washed off to prevent any disease, do about
the same thing and have a great crunching noise.
Another approach, besides just leaving the top of the box open, is to fill it
with old newspapers or other noisy and seal the box. Then cut a hole on each end
of the box. That keeps ferrets occupied for hours. They run in and out and never
seem to tire of this one.
Tubing
Ferrets are natural diggers. Therefore, giving them tubes to run through
provides the illusion of tunneling underground. Pet stores take advantage of
this by charging $20 for only six feet of tube. That's ridiculous, and you can
do it far better and cheaper.
There are actually two ways around this and both involve home-improvement
stores. The first is gutter extenders, which usually come in six-foot sections
for about $7. They can be twisted and manipulated multiple times and can be
interconnected. One of the ends is usually small so if your ferret is a little
fat, he or she may have some trouble making it through. Be sure, however, to
cover the sharp ends with some packaging tape.
The other option is roughly the same, just on a larger scale. A
home-improvement store should sell underground piping for irrigation systems.
This is usually located in their outdoor nursery, by the seasonal plants and
such. It comes in a variety of lengths, the smallest being 10 feet. It costs
only $5 a section that size (you can buy 100 feet for around $20-$30). The bonus
here is, just like the pet store, they sell attachments. By connecting them, you
can literally have your critters running throughout your home, popping out at
certain intervals thanks to the exits these attachments have.
If you go this route, be sure to make plenty of openings for the ferrets to
get in and out. If you don’t, it's possible they'll get scared and panic. Make
sure to make everything as twisted as you can, even make the pipes go over
“hills.”
With either gutter extenders or irrigation tubing, it’s easy to frequently
change things around. Try and judge how long it takes your little guy or gal to
become bored and then rearrange it. Otherwise, you have tubing all over the
place and no ferret playing with it.