Simple Road Design and Earthworks
Free and open source pattern design software
Electric Design Tool
very good CAD software
Open-Source Shoemaking
A math-inspired CAD program in haskell. CSG, bevels, and shells
Open source 3D software based on opencascade(CAD)
Open Source Planar Linkage Mechanism Simulation and Synthesis Software
Design your own pottery for 3D printing in full color
CT Soft is software designed to be used with Control Techniques Drives
Open Knowledge on engineering development.