Gears of course.

Angle of repose

Factories

Trains

Vision Command

Math

Space

Walking

Pendulums

Worm Gears for raising water?

Levers

Pulleys, Dropping weights, Light sensors.

Friction

 

Graphing

Copying graphs

Pendulum, graphing
 

Pressure
 

Visual

Remote Sensing

SEM over the Internet
 

Rube Golberg

The best and most complicated.

Many ideas so easy to get that would be good to implement in a
hands on, permanent site near the university.