For all of you, like myself, that spend a lot of time surfing the net for free card/paper ship models, I found the crown jewel! An Asian site called 3D Papermodel, has a seven page directory of free paper/card model ships! While, I will warn you that some of the links no longer work, a majority of them do. Plus the site has links to all kinds of free models. Go knock yourself out!
edit 10/16 – Bill Wills describes some great sites in his comment below. Please check it out for some additional models! Thanks Bill!