Some of the useful Open Source Tools of the day

Sweet Home 3D

An interior design application to draw house plans & arrange furniture; Sweet Home 3D is an interior design application that helps you to quickly draw the floor plan of your house, arrange furniture on it, and visit the results in 3D.

http://www.sweethome3d.com/

FreeMind

A premier mind-mapping software written in Java; A mind mapper, and at the same time an easy-to-operate hierarchical editor with strong emphasis on folding. These two are not really two different things, just two different descriptions of a single application. Often used for knowledge and content management.

http://freemind.sourceforge.net/wiki/index.php/Main_Page

gnuplot

A portable, multi-platform, command-line driven graphing utility, A famous scientific plotting package, features include 2D and 3D plotting, a huge number of output formats, interactive input or script-driven options, and a large set of scripted examples.

http://gnuplot.sourceforge.net/

GeoServer

GeoServer is an open source software server written in Java that allows users to share and edit geospatial data. Designed for interoperability, it publishes data from any major spatial data source using open standards: WMS, WFS, WCS, WPS and REST

http://geoserver.org/

LibreCAD

A free Open Source CAD application for Windows, Apple, and Linux; Features:

Reads DWG and DXF files

Writes DXF, SVG, PDF and more…

Custom toolbars and menus

Highly customizable appearance (GUI)

Advanced snapping system

Line, polyline, spline, circle, ellipse, text, dimension

Blocks and hatches

Plugin system

http://librecad.org/

matplotlib

Matplotlib is a python library for making publication quality plots using a syntax familiar to MATLAB users. Matplotlib uses numpy for numerics. Output formats include PDF, Postscript, SVG, and PNG, as well as a screen display.

http://matplotlib.org/

http://matplotlib.org/users/installing.html

gretl

gretl is a cross-platform software package for econometric analysis, written in the C programming language.

Easy, intuitive GUI

Sophisticated (OLS, MLE, GMM, system estimation)

Internationalized (10 languages besides English)

http://gretl.sourceforge.net/

FreeCAD (beta)

A parametric 3D CAD modeller; FreeCAD is a general purpose feature-based, parametric 3D modeller for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialities. It is 100% Open Source and extremely modular, allowing for very advanced extension and customization. FreeCAD is based on OpenCasCade, a powerful geometry kernel, features an Open Inventor-compliant 3D scene representation model provided by the Coin 3D library, and a broad Python API. The interface is built with Qt. FreeCAD runs exactly the same way on Windows, Mac OSX and Linux platforms.

http://www.freecadweb.org/