I've always been obsessed with the Real Simple paper constructionist, Matthew Sporzynski. David Brownings, an illustrator living in Bristol, has a similar talent with a little twist. Here's a sample of his work...
These are described on his site as boxes, but I'm not sure if they are usable or just amazingly cool.
Paper shoes...amazing.
Pop-up books are totally under-appreciated. I love the sense of grandiosity in this illustration.