Introducing ThoughtWriter: a complete set of programs to help you write stuff. The main focus is fiction, although you can use it for other things as well: writing letters, for instance.
ThoughtWriter is the combination of Edit4, which is based on Edit3, but utilizes Verbose¹, and ThoughtType4, a simple file format and markup language, vaguely inspired by Wiki markup languages. If you have the spell4py module installed (which is a Python binding for Hunspell, the spell checker included in Firefox 3 and OpenOffice.org), you can enable automatic spell checking.
Also included are a set of small programs (conveniently called in Edit4 by pressing Ctrl+P):
If you like the ThoughtType4 format and the tt42* converters, but don't want to (or can't) use Edit4: I have written a syntax file for nano. You can download it here.
Coming soon.
For Windows
Source (requires Python 2.4 or 2.5 and wxPython 2.8.7, not tested with other versions)
GitHub repository
¹ Verbose is an editing component (basically Scintilla), which supports different fonts, for a better WYSIWYG experience. See included documentation for more information on Verbose.
² It will probably not run on OSX. I have not tested it, and never will. If you made the necessary Mac-specific modification, please send me a patch.