Dr. Clue's X-Browser DHTML library.
Supports NS,IE,Opera,Neo-Planet browsers. Examples. Also includes windows help files.
url: www.drclue.net/beta/
JavaScript and DOM Factory
Visual browser checking for properties of JavaScript and DOM objects.
url: zvon.org/xxl/JSDOMFactory/
jsDOM API
The jsDOM project was created in order to develop a Javascript library for creating dynamic html components in browsers that support the DOM.
url: jsdomapi.sourceforge.net/jsdom/
netWindows
A DOM based DHTML API for widgets and web applications. Demos.
url: www.netwindows.org/
T-Menu
DXHTML W3C Compliant Menu system
url: www.cfoster.net/tmenu/
XPDOM
A W3C-DOM Level 2 compatibility layer to programming Dynamic HTML in standard DOM and exactly same way in any browser with DHTML capabilities: Navigator 4.x, MSIE 4.x, 5.x and Mozilla/Netscape 6 as reference implementation.
url: xpdom.sourceforge.net/html/index_frame.html