I saw today a great example of using XUL (XML User interface Language). The pointer is from Digg. It's an application that searches Amazon and displays results in an elegant way. It looks like an entire seperate program. Try it, it's amazing. If you are programmer, get a look to the source of the page: In firefox CTRL-U.

The URL of the application: http://www.faser.net/mab/chrome/content/mab.xul

Useful Links:
- Some examples from Google
- Wikipedia: XUL
- Wikipedia: Comparison of user interface markup languages