I’d be remiss to be writing about great freeware, yet ignore the program I’ve using to write with in the first place. Notepad++ is a text editor with the focus on the editing and maintainance of source code, but is well adapted to any plain-text usage.
The sheer number of options available are staggering. On top of a vast array of text filtering and coverting options, there are 44 built-in languages with the ability to define the behaviour of each or create new languages, zooming, code folding, colouring, back-up settings, macros. It’s futile to list them all. And if there’s not enough there, the community has provided an excellent selection of plugins.
For Windows developers, there’s no excuse to not be on board. Just remember the functions list plugin.