A Toy Crank
A "simple machine" made from a spool and a popsicle stick.
Ropes and Pulleys
A few toy devices you can make with ropes and pulleys from the hardware store.
A Paper Pinwheel
How to make a homemade, hand-held windmill.
A variety of toys you can buy or make to explore balancing and center of gravity
A Set Of Weighing Scales
Simple balances you can make with cheap, everyday household supplies
A Toy Spring Scale
Make a crude weighing device from simple parts.