As a web designer, and you can find a number of open source applications tremendously useful. The price tag of open source projects is 0$, but they are great for other reasons—one of the main reasons being the dedicated community that surrounds these projects. With the state of the economy, finding places in which you can conserve is a positive direction, and that direction should point you to open source alternatives.
Below are 30 excellent open source applications that many web designers live by. You will be educated on a great number of tools, including WYSIWYG, source code, image, and graphic editors. There are also some useful utilities that can better the production process and task management.
WYSIWYG & Source Code Editors
Bluefish Editor

This lightweight, speedy editor for programmers, as well as web designers, offer amazing wizards for documents in the HTML format, quickly batch-replacing source code with a search-and-replace option, and has great features for project management.
Amaya

This open-source web editor and browser is not only free, but it was developed by W3C (World Wide Web Consortium). It was originally a CSS/HTML editor but has now flourished into an XML-based system editor. Such systems are MathML and SVG.
Open BEXI HTML Builder

This open-source application is browser-based and creates HTML web pages. It does come with a CSS Color Picker that can be found built into the interface. It is widely considered to be a simple option for project management.
CSSED

CSSED is a GTK-2 Based CSS editor that is considered to be fully-featured. It comes with a plugin system, allowing for extensions.
NOTEPAD++

This is an incredibly popular Windows open-source text editor. It isn’t just for web designers! It also has a source code editor that supports HTML, CSS, JavaScript, and XML.
SeaMonkey

This all-in-one web browser that is parented by the Mozilla Foundation is powerful, yet simple when working with in-browser source code. Also called SeaMonkey Composer, it is an HTML editor.
jEdit

This text editor was designed for programmers, with the capabilities to run on Windows, Linux, and Mac. Also, it has highlighted syntax intended for HTML, CSS, JavaScript, XML, and more.
Image & Graphics Editors
GIMP

If you want to use one of the more popular open-source projects, then GIMP is definitely one to consider. It is feature-packed and serves as a graphic design suite and image editor. It even offers a PhotoShop alternative, Gimpshop. It is an extension that almost matches the interface that PhotoShop has.
Dia

For diagrams and flow charts, Dia is an excellent diagramming tool.
Inkscape

This open-source vector graphics editor rivals many commercial brands like CorelDRAW and Adobe Illustrator.
Karbon14

A part of KOffice, Karbon14 is a vector-based application that you can scale.
OpenOffice Draw

This tool is for drawing and diagramming. It comes as a piece of the OpenOffice software.
Skencil

This vector drawing application is recognized for its diagrams and illustrations. EPS formatting is available.
FontForge

FontForge is a useful open source font editor. Perfect for editing fonts for original designs.
mtPaint

This utility was developed to be simplistic and ideal for editing and painting. Mark Tyler is the creator.
ImageMagick

This is an image-editing suite that allows you to use bitmap-based formats to compose images. There are over 100 formats you can open and save as, which includes: JPG, SVG, PDF, and GIF.
Utilities
Cyberduck

This open-source FTP client is exceptional and designed for the Mac OS. For web application developers and web designers, they found special use with the support it has for Mosso Cloud files. Also, it has a built-in browser (Amazon S3) that makes it top-notch.
HTML TIDY

Not only is this utility free, but it is also perfect for optimizing and fixing HTML syntax.
FileZilla

When people look for an FTP client, this open-source client comes to mind. The supported OS is Mac, Linux, and Windows. It can also send files through a number of different protocols.
CamStudio

CamStudio is an open-source screen-capturing tool that is fully-featured. If you are requested to create a computer simulation for an activity like a website tour, then this is the tool that you need to be looking at.
WinSCP

Only for Windows, this FTP client is used for remote and local file transfers. The file manager is simple to use, allowing for easy navigation and file organizing.
Greenshot

Screenshots are oftentimes necessary for web designers. Usually, they are used for documentation and in-browser design presentations. This robust application is open source and free.
Firebug

This extremely versatile debugging tool is super useful. Learn and explore CSS markup and HTML.
ZScreen

This open-source screen-grabbing tool allows for automatic FTP screenshots. This function is exceptionally helpful for sharing and archiving any image.
Gallery

Take command of your repository for images. This web-based image gallery allows you to organize, access, and store image assets online.
Xournal

This simple ketching/note-taking tool allows you to use a tablet as a device permitted to input. This is a similar design to Windows Journals.
With the open-source tools and utilities, you can easily organize, manage, and follow through with any project you may have. These are the favored choices among many in the industry and have all received high marks and reviews from many users.