I don’t do CAD or 3D printing, but this software at least looks promising from my armchair. It’s an open source CAD/CAE app based on OpenCasCade, QT, and Python. It offers features like macro recording, the ability to run as a server and dynamically load application extensions, and it runs on Windows, Linux, and Mac. One of the many cool features it offers is 100% scriptable objects in Python:

Besides the standard object types such as annotations, meshes and parts objects, FreeCAD also offers the amazing possibility to build 100% python-scripted objects, called Python Features. Those objects will behave exactly as any other FreeCAD object, can be saved in a document and opened on any other installation of FreeCAD, since the python code that defines the object is also saved in the document.

The project is still in alpha. The only official builds are in Windows and 32-bit Debian Linux, but you can download (from their SourceForge site) unofficial builds for AMD-based 64-bit Debian/Ubuntu, openSUSE. and Intel Mac OS X.