I made a few of these about 10 years ago. They used to come printed on flat card stock (a few still do) and you cut them out and glued them together with Elmer's white glue. It's amazing how good they look. The subject matter is strong on airplanes but you can find paper models of most anything. It is common for the models to be pdf files that you download and print out on your own printer. The cost is usually pretty modest and there are many free downloads. Great fun.

Yamaha Paper Craft

Fiddler's Green

Paper Paradise

Paper Shipwright

Paper Models of Polyhedra

Card Modeling FAQ