Well, without Emacs, I wonder what I would have coded and how much!
Once you know how to configure and use it correctly and find the modes for your needs, it's the ultimate toolbox for any text editing you need to do, from coding to document writing.
SPIP has been the web site publishing software I have been using for over 6 years now.
It has kept evolving and is now a strongly multilingual editorial content management. Its default release is ready for use for anyone, without knowledge of web development, php, mysql, etc. However, it is also backed by a powerful templating system and plugin architecture that enables easy extension of its features.
SPIP is a great software with an active and friendly community and the development version seems to be aligned to offer even more great features.
Great tool to process camera RAW photos, with many options. It's still easy to use, does what it says it does really well and is sometime better than the closed codebase shipped with the cameras.
The gimp plugin is also very practical.
(I use it under OSX)
This is a great extension for Firefox and is the main reason I use this browser over others. It offers a very nice way to extend and hack your favourite sites and add novel feature to web content.
I use this as a command line tool to check exif and do time corrections too, it's a great tool and supports more than images, hell, it will work with pdf metadata, video, mp3, etc...
It also a very easy to use perl library, so it's very nice to program scripts that would need to access the file metadata.