You'll find on this page some examples which respect rules of the XUL Challenge 2004.
This examples use Mozilla Technologies, such as XUL, the real XUL language, the XUL of Mozilla (XUL is not a generic term for XML user interface language, contrary to what organizer of XUL challenge 2004 says; XUL is the name of the XML user interface interface language of Mozilla.org, one of the first of this kind of language).
You need the Mozilla browser to run this examples. You can download zip package of them.
(Last modification : may 24,2004)
It use simply XUL, with a CSS stylesheet for design and javascript for the behaviour.
The counter is now embedded in an XBL component, so you can reuse it easily in all application you want.
Because i haven't enough time to develop a bigger example that show more disruptive innovation, i just invite you to open Mozilla browser and see it : its user interface is made entirely in XUL, with XBL components, CSS (for design/themes), Javascript 1.5 for behaviour, and XPCOM for complex and reusable processing. ( XPCOM = cross-plateform componant in C++, javascript; other language can be used, like Python...)
For more information about XUL, XBL etc, see http://www.xulplanet.com or http://xulfr.org (french).
Author of this examples : Laurent Jouanneau