When developing for the web, it's important to check your website using several different web browsers. Microsoft's Internet Explorer (IE) is notorious for displaying or interpreting your web pages in ways that are slightly different than most other web browsers.
Firefox generally less prone to hacking than IE
FireFTP Use this Firefox add-on or the standalone Filezilla (below) to transfer files to your website
View Source Chart Firefox plug-in gives you a nice graphical view of your
HTML containers, making it useful for debugging missing tags.
Firebug This Firefox plug-in is an HTML/CSS/Javascript debugger
Google Chrome More streamlined than IE or Firefox
Safari Apple's browser for the Mac, but there is a Windows version that's pretty cool
Opera This Norwegian web browser has been popular in some regions for quite a long time and it's
on the forefront of support for many HTML5 features.
Opera Portable This is the Portable Apps version of Opera. Copy it to a flash drive and run it on any
computer without having to install it. If you haven't checked out PortableApps.com for other apps that you can run off a flash drive, you should!
IETester This is a handy tool to see how your websites will render under the various versions of
Internet Explorer from 5.5 through present.
Notepad++ This open-source programmer's text editor color codes your HTML and CSS
(and other computer languages) and has a lot of nice editing features.
Notepad++ Portable This is the Portable Apps build of Notepad++ to run off your flash drive.
Text Wrangler This is a Macintosh programmer's text editor that does a similarly good job
of color-coding and formatting various computer languages.
Filezilla FTP client software for transfering files to your website.
Filezilla Portable This is the Portable Apps build of Filezilla. Take it with you and run it
off your flash drive.
Apache Mobile web server
Yes, you can spend hundreds of dollars for Adobe Photoshop, but the following free image editors do about 90% of what you ever need for basic image processing. They're fast, too. Although I own Photoshop, I prefer to use Photofiltre or Paint.NET whenever possible. I only pull out Photoshop when I absolutely need one of its features.
Photofiltre nice, fast image editor for most common tasks
Paint.NET more features, and allows multiple layers
GIMP originally a Linux image editor that incorporates many Photoshop-like features,
it keeps getting better and it is now available in Mac and Windows distributions
PHP manual from php.net
PHP Designer Personal php IDE