PiratePad is a web-based collaborative real-time editor, allows authors to simultaneously edit a text document, and to see participants' edits in real-time.
TinyMCE (Tiny Moxiecode Content Editor) is a platform-independent, browser-based WYSIWYG editor control, written in JavaScript and released as open-source sof…
StackEdit is a full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.