Although I still do not know XML and XQuery as well as I’d like, I’m learning.
One of my favorite resources is Michael Rys blog. For example, the July 13 posting is exceptionally good and will point you to many other valuable resources (http://sqljunkies.com/WebLog/mrys/archive/2005/07/13/16044.aspx).
In addition to Michael’s blog, you should look at this white paper that introduces XQuery support in SQL Server 2005 (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsql90/html/sql2k5_xqueryintro.asp).
Let me know if this is of any value to you.