DIY Cardboard furniture That doesn't look like it's made from cardboard! We've had some great posts on cardboard furniture you can buy that doesn't LOOK like cardboard, but most DIY options resemble the brown recyclable stuff.
Some pretty awesome book shelves. I personally want floor to ceiling shelves covering at least two walls in my spare bedroom. until I upgrade from condo to a house with a full-blown library / reading-n-nook room :D