People have asked me what tools I use, so I may as well make a list. All of these programs should be either pre-installed or available in your distro's repositories through your package manager.

If you don't have Linux (or Mac -- these should run on Macs in X11 mode if you have the QT library installed), Ubuntu is free and easy.

Kompare - A nice visual way to see the differences between two files or two directories. It's the same idea as the WSN File comparison tool, but easier to read. Also has an automatic patch tool but I haven't tried that.

KFileReplace - A search replace tool which is really useful when I want to change all instances of x in a directory to y.

KRuler - A screen ruler, for those times when you need to know just how many pixels wide/tall something is.

KColorChooser - Pick a color on your screen and it'll show you the hexadecimal value for use in your stylesheet.

gPHPedit - Fast-loading PHP editor. It's clean and simple.

Eclipse - IBM's integrated development environment includes a plugin for PHP. Very feature-filled, though it's overkill for most people's needs.

KWrite - KDE's standard text editor has HTML syntax highlighting and can locate line numbers, along with search/replace, making it useful for quick template changes and the like.

The GIMP - It's not the most intuitive image editor, but it's powerful, and I've gotten used to it over the years. If it weren't for momentum I might like Krita better.

Xara Xtreme - It's supposed to be a powerful vector-based graphics program, but I don't seem to be smart enough to learn it.

Nvu and Quanta Plus - I don't use either of these much, but they'd be useful for those who don't like hand-coding HTML. Nvu is a WYSIWYG editor that keeps the code neatly validating, Quanta is a non-WYSIWYG development environment that'll manage whole projects for you and provides lots of shortcuts and wizards for creating HTML.

Konqueror - Using it as a browser it offers the handy ability to search for text in your templates. It can also change the user agent to googlebot and back with a click, handy for testing spider-related features. As well, it uses the same KHTML rendering engine as Safari so by testing Konqueror you can ensure your site looks good for the 3-4% of people who use Safari without needing to buy a Mac.

gFTP and Konqueror - Both work as nice FTP clients with recursive deletions and all. Decide which layout you prefer.

basKet - It's a great place to drop notes and to-do lists while I work.

Opera - This web browser has a lot of web developer tools, like the ability to validate pages with a click or to show various levels of page elements in user mode.