Qooxdoo

Qooxdoo is an impressive javascript framework; you can develop a sophisticated interface without writing any HTML.

The Eclipse Rap project is an interesting project that wraps Qooxdoo in a SWT Java API; you develop in Java and the Eclipse plugin hides Javascript completely.

The drawback with qooxdoo is that it is a relatively big download and it is entirely code driven; a declarative approach to defining an interface (e.g HTML, XUL or XAML) is a must for designers and is probably easier for programmers.