Windows/Mac/Linux: If you're a coder and haven't tried the free, cross-platform text editor Komodo Edit yet, you may be in for a treat. Komodo Edit supports a wide range of scripting languages and boasts powerful customisation and extension options for easier coding.
Everyone has their favourite text editor. Not too long ago we picked Notepad++ as best for Windows and TextMate for Mac OS X, but if you want an editor that you can jump from Windows to Mac to Linux (and back) with -- in one consistent and clear interface, Komodo Edit is your best choice.
It might not be as fast, simple or as lightweight as Notepad++ (or TextWrangler), but Komodo makes up for it with IDE-like features like grouping files and specific code into projects. Komodo Edit's toolbox in the right panel lets you quickly access frequently used snippets, macros and commands to really speed up your workflow (I use it for snippets of awkward XML character encodings).
Another really notable feature is Komodo Edit's plugin system. These Firefox-like extensions and add-ons enable you to customise the program to your needs. You can add lists of classes and functions for your programming language, for example, to the sidebar, support for a specific framework, or extensions for things like colour-coding tabs or closing multiple tabs at once.
A host of other built-in Komodo Edit features, like syncing to and editing files on remote servers are also useful, but if you need even more development features, there's a more robust (and not free) Komodo IDE. Many people find Komodo Edit more than enough for their needs, though.