Michael and I have different backgrounds: he is the founder and the editor of a popular technical site and I am just a developer ;) So do not compare lists.
Here is my list of applications, in alphabetical order, I used often. And to make it consistent with Michael's post, the list is followed by a comment for each tool.
For programmers or English writers, keyboards with the US layout are just fine. If you use another layout, then it is a compromise between being able to generate specific characters and staying efficient. AllChars is a Windows tool that can generate any Unicode character with few key sequences (like Ctrl+e+e for €). It is fully customizable and support even macros.
This is the tool used to publish this blog. I have not invest enough time in customizing the page layout, but I know I can easily do it later and updates will be propagated to all posts. A good and efficient tool, IMHO.
DabbleBoard is a tool I blogged about in a post about Effective Communication principles.
Dropbox is a composed of plugins to install on your machines (Windows and MacOS) and a website which host your virtual folders. It is a silent tool, working smoothly, and synchronizing folders in background. I use it in conjunction with KeePass to backup my sensitive information.
Having been a Web application developer for a long time, I adopted Firefox (then know as Firebird) in 2003. With the introduction of the Firebug extension (in 2005), it became with primary browser and it had never lost this status. Its early integration of Google search was also a serious advantage. These days, with the faviconize extension and Firefox ability to start with the previous configuration, my browser always starts with: iGoogle, GMail, Google Calendar.
I started to use FriendFeed at its early stages, mainly because it offered the possibility to share information from Web page I can visit randomly. Because few months after its introduction, Google Reader added the Share with note function, I stopped using FriendFeed... until recently when I have invited to a private room: this is a pretty nice service for offline chats. It is not as heavy as e-mails and not as disruptive as instant messages.
I never the budget and training for Adobe Photoshop. So I started using Gimp. If you can pass over its weird interface (too many windows, IMO), Gimp offer tons of features for Web application developers: to adjust pictures, to generate textures, to resize images, etc. And there are plenty of free tutorials on the Web.
Git As a developer, I always want to put my code into a source control system. It is not just because I am afraid that my laptop crashes, then wasting hours of work. It is mainly because I want to keep track of the update history. At work, over the years, I used ClearCase, CVS, and Subversion. For my personal development, I used Subversion a lot and now I use Git.
GMail When I started working, I dealt with many machines and I hated having to start one just to look at a specific inbox. With GMail, my account is available anywhere. When I read Turn Gmail Into Your Personal Nerve Center, I started to use GMail as my knowledge database.
Google Calendar My first job in Montréal, Canada, was with a small company named Steltor (bought few years later by Oracle). The core business was the development of a distributed calendar system (servers in cluster, native clients, web client, mobile client, etc.). Since then, I am used to tracking my work with an electronic calendar. Google Calendar and its ability to mix many agendas is excellent.
Google Reader In the old day, reading blogs was time consuming and annoying because of the ad banners. With the introduction of Google Reader, reading them from one central place while just using keystrokes was a pleasure. With the introduction of the Share this feature, I became to be a media myself. The Share with note function is an quite recent addition that allows me to point posts that are more important to me.
Google Search Google Search is an amazing tool: recently, I was trying to find a solution to a tough technical problem and I found it thanks to Google Search which pointed toward a blog post written the same day, just few hours before, in Europe! Incredible... When I give a conference into universities, I often say: “If I asked a question today and you have no clue about the response, that's fine. If you still have no clue tomorrow, you're in trouble...”
KeePass KeePass is an open source Password Safe. I use it in conjunction with Dropbox. Much usable that PGP/GPG in the sense I don't have to save the decrypted file and then being at risk if I forget to wipe this copy from disk.
LinkedIn I started using LinkedIn when a wonderful team I worked with at Oracle exploded because of stupid political decision. Then some friends left to go with Google, one colleague went to Adobe, etc., and LinkedIn was the tool to stay connected. Since then, LinkedIn allowed to get many job propositions, like Compuware's one I accepted. I have been also able to retrieve friends I had in France, even one I may engage a partnership with.
VirtualBox Developing software requires sometimes specific configurations. Testing them requires always specific configurations (at least to replay always the same test cases every time the source control system, like Git, is updated). There are the famous VMWare products (Workstation, Player, ESX) and Microsoft VirtualPC. VirtualBox is an open source product provided by SUN Microsystems, and it has nice features while being powerful.
YouTube and Google Video YouTube is famous because of fun videos. But it also hosts technical videos.
I hope it helps,