CKEditor - Real-time collaborative future-ready rich text editor
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.
GitHub Flavored Markdown - GitHub uses "GitHub Flavored Markdown," or GFM, across the site--in issues, comments, and...
Trumbowyg - Feature-packed WYSIWYG editor in only 15kB of JavaScript
Texy! - Texy! is a lightweight markup language as well as converter of this format to XHTML, in a form of a...