How to build a castle for your cat!! It sounds interesting for entertaining
indoor cats - a castle of cardboard boxes that you build yourself. I was a
bit sceptical, afraid that the whole thing may collapse on the cat but it
may be worthwhile. It's at:

http://www.43things.com/entries/view/1269183

My cat isn't into things like that. He goes out during the day (it's a safe
environment) & sleeps most of the night. He has a few catnip toys which he
occasionally plays with - usually only in the winter & on rainy days when he
doesn't want to go out. He's very picky with his toys. I often see things I
think he may like, bring them home and introduce them to him. Four out of
every five toys I buy he completely rejects. He keeps his interest for more
than a day in only half of those which are left. The local cat rescue
shelter gets a lot of toy donations from me! Yet in the garden he'll chase,
bite & kick anything - grass, twigs, leaves, ...!!