Some useful places to visit...
Autodesk AutoCAD is but one of Autodesk’s massive portfolio of programmes
Vectorworks Very popular software amongst lighting designers (and landscape gardeners)
AutoStage AutoCAD plus lighting, sound, AV and so on. Currently only in German but an English version is on its way
DraftSight Popular AutoCAD alternative as already mentioned
SketchUp Not really a purely CAD programme but very useful 3D tool.
Looking online for various ‘Top Free CAD programmes’ will find you many others - happy hunting!
Blocks, Symbols etc
CADBlocks.net From planes to trees to people to furniture, over 5000 free drawings to use
CADBlocksFree.net Free and paid for Blocks in dwg and other formats
Modelbox Lantern symbols and a vast library of UK and other Theatres available on a licence basis
Cue1.net Selection of older lantern and other Blocks
Meyer Another Loudspeaker manufacturer, CAD files can be found in Resources for each product
DigiCo Sound Console company- CAD files with each product (DXF)
They are of varying quality and all need some work to turn them into the classic outline that most people want. Other manufacturers don’t provide either DWG or DXF file formats and so aren’t included here
ABTT Association of British Theatre Technicians
ALD Association of Lighting Designers
ASD Association of Sound Designers
PLASA Professional Lighting And Sound Associaton
PMF Production Managers Forum
SBTD The Society of British Theatre Designers
SMA Stage Management Association
AUGI Autodesk Users Group International