DIY Stuff Old tires can easily be found,cleanFree Cat Tree Plans DIY cat stratching tree // Katzen Kratzbaum Birke selbst gemacht
The Refined Feline Catemporary Cat Corner in White
probably not so good for an apartment though. (Also brings up the question about cats deciding to hack up a hairball from above.
DIY Frosta cat tree (via ikeahackers)