Paper and cardboard are readily available and pretty cheap -- so they're great for making all sorts of toys. Here is a partial list of toys that can be made and techniques that can be used to make toys. -- Architectural and railroad models, books, boxes, Christmas tree ornaments, constructions and assemblages, greeting cards and envelopes, corrugated cardboard stuff --- castles and houses, costumes and hats, decorations of all types, dioramas, displays and signs, dollhouses, drawings and paintings, magic paraphrenalia, masks, medallions, mobiles, models of all types, paper cutting, paper chains and garlands, paper dolls, paper folding (origami), paper mache, paper planes, paper sculpture, paper snowflakes, printmaking methods -- various, pop-ups, props (for shows), puppets, puzzles, rubber stamping, sets (for shows), wrapping paper, etc.

HOOPSTER -- An easy-to-make flying thingy. You might find it easier to put this together with a hot melt glue gun instead of tape. 
Visit: http://www.exploratorium.edu/science_explorer/hoopster.html

ROTO-COPTER -- a little paper toy that can be made in minutes. 
Visit: http://www.exploratorium.edu/science_explorer/roto-copter.html

PAPER BRIDGES -- This site shows how to make simple paper bridges out of cards. A good project for an engineer-in-training. 
Visit: http://www.exploratorium.edu/science_explorer/card_bridge.html

SPINNING BLIMP -- here's a website that shows out how to make a simple SPINNING BLIMP.
Visit: http://www.exploratorium.edu/science_explorer/spinning_blimps.html

THIS-TO-THAT --- This has to be one of the most interesting applications we've seen on the net. We wish we'd have thought of it ourselves. This simple site allows you to input 2 simple multiple choice parameters...One is a "This" and one is a "That" meaning, I want to glue "This" to "That". It then comes back with a quick response telling you the best method in which to do so. For example, we wanted to glue "Paper" to "Leather" it gave us the following reply >>

We recommend: 3M 77 - A less toxic alternative is: Sobo or Rhoplex - But it would make the paper wrinkle. For a non-toxic and absolutely wrinkle free result, we recommend: Yamato Sticking Paste.

All of these answers come with links to pages with detailed information on the products mentioned. Visit: http://www.thistothat.com/