MarkdownDeep is an open-source (read license) implementation of the increasingly popular web publishing syntax Markdown. MarkdownDeep provides a high performance implementation for ASP.NET web-servers along with a compatible JavaScript implementation for client side use.

markItUp! is a JavaScript plugin built on the jQuery library. It allows you to turn any textarea into a markup editor. Html, Textile, Wiki Syntax, Markdown, BBcode or even your own Markup system can be easily implemented. http://markitup.jaysalvat.com/home/

Mercury Editor is a fully featured editor much like TinyMCE or CKEditor, but with a different usage paradigm. It expects that an entire page is something that can be editable, and allows different types of editable regions to be specified. It displays a single toolbar for every region on the page, and uses the HTML5 ...