XUL available application, examples, demo. development?

It looks like XUL is the way to go for user interfaces.

What are the available application, examples, demo. development systems etc
that use XUL? It would be nice to see XUL in action.

There is obviously no XUL mailing list, but are there many people working
with XUL?

Is there some sites where there is more details on application user
interfaces, todate I have seen only  XUL Tutorial
http://www.xulplanet.com/tutorials/xultu/
XPToolkit Architecture
http://www.mozilla.org/xpfe/aom/AOM.html

The GNUe Form Definition Language
http://gnue.org/docs/GNUeFormsTechRef/x303.html