There are countless workshops and no doubt I will have forgotten some of them but here is a list of the more popular ones.....
Making vehicles of various types: Land yachts, balloon cars, elastic band cars, rocket (air jet) cars, electric cars, Including bodywork and streamlining, cable cars/aerial runways, solar powered cars and solar service stations.
Rockets and flight, rocket rescue challenge.
Bridges of many types including very large scale bridges as event showpieces
Structures: Towers, stadium, cranes, fairgrounds (and mechanisms), playgrounds.
Mechanisms: Cranes, crank and cam toys, levers, winding toys, ancient siege machines eg. ballistas and siege towers.
Electricity projects: Torches, buzzer games, switches and alarms, motorised projects, electromagnets and magnet games.
Pneumatics and Hydraulics using syringes.
Shadow puppet theatres
Sound: musical instruments and sound effects.
Picture frames and more besides: multi-frames, diarama, moving pictures.
Toys from other civilisations eg. Aztecs, Myans.
Recycling plastic milk bottles - design challenge
Paper and card shapes falling through the air- ‘helcopters and fliers’