I consider myself a web developer, not necessarily a web designer, but certainly a developer. As such, I do not require the latest Adobe suite of programs to get the job done. There are plenty of open source Linux applications that can help accomplish this for free.
I see five different areas of software that I use during development. I first, of course, need a development environment to generate my code. I need software to manipulate images that will be used in my sites. I need a program to encode videos into web friendly formats. After all of this, I need to get my files onto the web server. Lastly I need to be able to view the completed work to see how it turned out and determine where I need to tweak my code.
jEdit is my IDE of choice. I have tried others and could never find one the encompassed all of my needs. jEdit's robust module system allows enough expansion to cover almost any developers' needs. Most important of these is the FTP plugin for editing code directly on the server. The CSS auto complete feature is a nice plus too, though it was never a requirement that I had set out to find.
The GIMP is a no brainer here. It is the standard for image editing and creation in a Linux environment. A lot of people say that is severely handicapped in comparison to Photoshop. I am not a professional designer but have been able to do everything I have ever needed to do to an image with The GIMP. A legal version of Photoshop would cost me over $600, that's a cost I can't really justify for an individual – sans self-employed, professional designers. If you are into design that much, then you are probably a Mac elitist anyway – so why are you using Linux? I have found that I can almost always follow a good Photoshop tutorial I have found on the web and mimic it using The GIMP with equal results. I may have to add a couple more steps to the process, but that is fine considering I did not have to fork over any money to do it. Note: This argument does not acknowledge the option of Photoshop piracy.
MPlayer's movie encoder is fast on the command line. I am able to take nearly any video format and then resize it and convert it into a Flash video. That makes it have a smaller filesize and also ensures that it will be in a format that is usable to most visitors.
I can edit my code directly on the server with jEdit, but I have to get my images, videos and whatever else I am delivering up on the server. gFTP is the only FTP client I have ever used in Linux. I have never found a reason to look elsewhere because it does everything I need. It allows bookmarking so I can connect to my sites with a click and get my files up.
Of course I use Firefox to test sites with. It is also my main browser for surfing the web. But Firefox is not representative of the users who will be visiting sites. Unfortunately most people still use Microsoft's travesty of a browser – Internet Explorer. Luckily I do not need to keep that OS available as an option on my machines just to use that broken browser. IEs4Linux is a script developed by Sérgio Lopes that enables the download and installation of IE 5, 5.5 and 6 through Wine, the Windows emulator. I do not use all of the versions of IE that he makes available, just IE 6 and 7. To get IE 7 you currently need to use the beta version of IEs4Linux.