Scilab

Scilab is free and open source software for numerical computation providing a powerful computing environment for engineering and scientific applications.
Scilab is released as open source under the CeCILL license (GPL compatible), and is available for download free of charge. Scilab is available under GNU/Linux, Mac OS X and Windows XP/Vista/7/8 (see system requirements).

What is Scilab ?
Scilab includes hundreds of mathematical functions. It has a high level programming language allowing access to advanced data structures, 2-D and 3-D graphical functions.
A large number of functionalities is included in Scilab:

EAGLE PCB Desing

Schematic Editor
The goal of the schematic is to provide documentation about the design, allowing others to easily understand your design intent. EAGLE comes with thousands of pre-made parts that simplify your schematic capture tasks.
Layout Editor
You can locate your components accurately and route copper traces between them. EAGLE's Layout editor includes sophisticated features such as assembly variants, differential pair routing and much more.
Autorouter
The autorouter can be guided by adjusting its cost factors to control its routing behavior producing useful results in no time. The Autorouter protects prerouted traces giving you full control over what nets need to be manually routed and which can be routed automatically.
Download

KiCAD

A full Getting Started guide is included in the KiCad documentation, in multiple languages. This covers the process of creating and completing a simple project. We recommend that all new users read this first, in order to learn the basics.

Quick KiCad Summary
This is a quick summary of how KiCad functions. More details can be found in the full documentation.

Libraries
KiCad uses two separate types of library: symbols (.lib) and footprints (.pretty). Symbols are used to draw the schematic. Once symbols have been placed into the schematic, footprints are assigned to them, and then these are used to lay out the circuit board.

BRL-CAD

BRL-CAD is a powerful open source cross-platform solid modeling system that includes interactive geometry editing, high-performance ray-tracing for rendering and geometric analysis, a system performance analysis benchmark suite, geometry libraries for application developers, and more than 30 years of active development.

BRL-CAD is a powerful cross-platform Open Source combinatorial Constructive Solid Geometry (CSG) solid modeling system that includes interactive 3D solid geometry editing, high-performance ray-tracing support for rendering and geometric analysis, network-distributed framebuffer support, image and signal-processing tools, path-tracing and photon mapping support for realistic image synthesis, a system performance analysis benchmark suite, an embedded scripting interface, and libraries for robust high-performance geometric representation and analysis.

A9CAD

A general purpose 2-dimensional CAD program. It supports industry standard DWG/DXF drawing formats. With A9CAD you can draw shapes such as line, rectangle, circle, poly-line, text and dimension; performing drawing modifications like move, scale, rotate, explode, trim, fillet and mirror; edit color, fill mode, line type and line width; change entity attributes via properties window. Manage drawing styles and settings and configure drawing environments.

Geomagic Design

Driving Engineering Forward with Geomagic Design
With comprehensive 3D CAD tools for design, engineering and preparation for manufacturing, Geomagic Design empowers rapid, accurate product development in an easy-to-use environment.

At a highly affordable price point, Geomagic Design delivers top-end tools at lower cost, including comprehensive assembly, parametric and direct editing tools, 2D documentation, sheet metal design, motion analysis and integrated CAD data sharing tools.

Open casecade

Open Cascade is an Information Technology Company of Capgemini, Open Cascade provides services in the domain of scientific and technical computing and simulation tools.

Open Cascade is primarily known to public for its Open Source platforms the company has been maintaining, improving and distributing free of charge for many years:

Open Cascade Technology (OCCT) for 3D surface and solid modeling, visualization, data exchange and rapid application development
Salome (software) - free software that provides a generic platform for Pre- and Post-Processing for numerical simulation.