Andy Otwell gathers up some interesting component/pattern-based approaches to UI design:
"The idea here is this: many application user interfaces are (or should be) essentially modular groups of widgets or components and containers for grouping components. Given that strict structure, a UI designer can write an XML document that refers to a library of predefined interaction components, style it with a CSS-like stylesheet, and describe its behavior with some code written in a scripting language (like Javascript or Actionscript). Although there are syntax differences between the four models above, the basic idea is the same."
The forthcoming Flash MX, Flex, one looks most interesting, given MX’s ability to build applications (which Andy notes the web browser struggles with, limited to POSTs and GETs). The Flash component hierarchy looks useful. Again Andy’s smart enough to note the limits of such a tightly component-based, pattern-based architecture, but also the obvious advantages for quickly building reliable, consistent interfaces.