FreeCAD is a general purpose parametric 3D CAD modeler. The development is completely Open Source (LGPL License). FreeCAD is aimed directly at mechanical engineering and product design but also fits in a wider range of uses around engineering, such as architecture or other engineering specialties.
FreeCAD is fully multi-platform, and currently runs flawlessly on Windows and Linux/Unix and Mac OSX systems, with the exact same look and functionality on all platforms.
Installing FreeCAD from the console on Ubuntu 14.04
Type (or copy-paste) these commands in a console to add the PPA and install FreeCAD along with the documentation:
sudo add-apt-repository ppa:freecad-maintainers/freecad-stable
sudo apt-get update sudo apt-get upgrade sudo apt-get install freecad freecad-doc
Now, FreeCAD is installed on your system. Start working with this.