Modern Wargamers may be interested in this paper model of the familiar yellow schoolbus.
Phillip Fickling has a paper model of a submarine that may be of use for victorian science fiction fans. Click on the free model link.
This three story european paper building model looks like it would work pretty good for 15mm miniature wargames. Players of Flames of War should take a look and see if it fits in with their tabletop layouts.
Martin Gumbold offers a nice paper model of a two story, European “good shed” — what I would call a warehouse, because of the loading dock. There is no apparent scale, but I downloaded it and sized it up, and think it would work very well for 20mm, and pretty well for 25mm – 28mm figures. You could use it for a variety of periods, because there are no obvious things to date it.
Ravensblight has a free paper model of a hearse and coffins. Because you can have your printer resize these, they can be used for any number of scales and games.