OmniHelp is a cross-platform, browser-independent, tri-pane help viewer built in pure JavaScript and CSS with HTML 4. Some functions (such as help embedding) may in the future be in Java, C, or C++; CSH is fully supported. All code is under the LGPL.
An open source cross-browser WYSIWYG editor that's packed with every rich-text editing feature you need. Setting up openWYSIWYG is so easy, you can quickly turn any TextArea into a powerful WYSIWYG editor with just a few simple lines of code.
Miller is a javascript component (cross-browser) that aims to enable web developers to make any html component editable. Miller offers inline, rich text editing. Miller uses dom manipulation to do this in order to create true wysiwyg experience.