Contraptor is a ‘DIY open source construction set for experimental personal fabrication, desktop manufacturing, prototyping and bootstrapping’. The site refers to the possibility of building robots and 3d Printers but for most this will be a handy means of building any mechanical system that might otherwise require bespoke prefab manufacturing.
Examples show a CNC Lathe/Router and an XY Plotter. This is rather more community driven attempt at low level Open Source Hardware design that is nonetheless capable of sophisticated outcomes.