Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
GitHub Flavored Markdown - GitHub uses "GitHub Flavored Markdown," or GFM, across the site--in issues, comments, and...
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Texy! - Texy! is a lightweight markup language as well as converter of this format to XHTML, in a form of a...
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.