Backyard Ballistics: Build Potato Cannons, Paper Match Rockets, Cincinnati Fire Kites, Tennis Ball Mortars, and More Dynamite Devices by William Gurstelle He has lots of fun project books.
Qwirkle Board Game MindWare
Plastic you can shape with your bare hands.
City Dollhouse Kit by Lille Huset
MindWare KEVA Contraptions
Deluxekit bits project 0016lr
Look what I found at UncommonGoods: Stop Motion Claymation Kit for EUR
LEGO Architecture Studio 21050 Playset LEGO
Engino Mechanical Series - Gears