I built a bunch of shanty huts recently, based on a thread I saw here - this star wars one
http://leadadventureforum.com/index.php?topic=86856.45I tried the dampening method he mentions in a reply to me on the next page, but all it gave me was soggy cardboard
What I found worked was just to very carefully peel off one of the paper layers. The boxes I tried with (probably Amazon packaging) peeled off completely intact. The secret was to peel back all the way down the first row. Once that one was done the rest came apart with little pressure. However, take your time. A craft knife was also handy to prise up some pieces that were reluctant to move.
I did a couple of tests where I removed the paper from both sides of the card, leaving just the corrugations. However, it was far too weak to stand up. It may have been better soaked in superglue to harden it, but I found that the huts only needed corrugations on the outside, so I didn't pursue the issue.
The end result of the peeling was slightly untidy, but, hey - shanty town