What can turn out to be a complex design can become simple if its represented via a good set of diagrams. Diagrams can simplify complexity in your software design. Diagramming tools are used to create flow charts and business diagrams. While Microsoft Visio is one of the best diagramming tool that is commercially available, there are free diagramming tools that are equally good and lets you create professional looking diagrams.
Here are some of the best diagramming tools that are available for free:
Dia is free and open source diagramming software, developed as part of the GNOME projects. Dia is inspired by the commercial Windows program ‘Visio’, though more geared towards informal diagrams for casual use. It can be used to draw many different kinds of diagrams. It currently has special objects to help draw entity relationship diagrams, UML diagrams, flowcharts, network diagrams, and many other diagrams. It is also possible to add support for new shapes by writing simple XML files, using a subset of SVG to draw the shape.
Its available for GNU/Linux, Unix and Windows. Download the software here.
2. ARIS Express
ARIS Express is a free-of-charge modeling tool for business process analysis and management. ARIS Express is the first free business process modeling software. ARIS Express is the perfect tool for starting with Business Process Management. It’s easy to install and allows intuitive and fast process modeling.
Its available for Windows, Mac OS X and Linux. Download the software here.
Inkscape is an open source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format. It is very easy to edit nodes, perform complex path operations, trace bitmaps and much more.
The software is available for Windows and Mac OS X. Download the software here.
4. ADONIS:Community Edition
ADONIS:Community Edition is a free tool for professional business process management. It lets you to easily model your processes and organisational resources to document the status quo, show the big picture, and design changes.
You can download the software here.
Kivio is a free and open source flowcharting and diagramming application for the KOffice application suite, and has a user interface that is similar to Microsoft Visio. It enables you to create network diagrams, organisation charts, flowcharts and more.
The software is available for Windows, Mac OS X and Linux. Download the software here.
6. OpenOffice.org Draw
OpenOffice.org Draw is a vector graphics editor that is part of the OpenOffice.org office suite. It provides shapes, connectors between shapes and are available in a range of line styles and facilitate building drawings such as flowchart. It includes many features found in desktop software like Microsoft Visio.
Download the software here.
yEd is a free general-purpose diagramming software with a multi-document interfacey. It is a powerful diagram editor that can be used to quickly and effectively generate high-quality drawings of diagrams. Using yED you can create your diagrams manually or import your external data for analysis and auto-magically arrange even large data sets by just pressing a button.
Download the software here.