EpicEditor - An embeddable JavaScript Markdown editor with split fullscreen editing, live previewing, automatic draft saving, offline support, and more.
jsoneditor - A web-based tool to view, edit and format JSON.
vim.js - JavaScript port of Vim with a persistent ~/.vimrc.
wysihtml5 - Open source rich text editor based on HTML5 and the progressive-enhancement approach. Uses a sophisticated security concept and aims to generate fully valid HTML5 markup by preventing unmaintainable tag soups and inline styles.
raptor-editor - Raptor, an HTML5 WYSIWYG content editor!
popline - Popline is an HTML5 Rich-Text-Editor Toolbar.