Uche Ogbuji's XML.com article on
The State of the Python-XML Art, 2003 is good guide for people unfamiliar with Python's XML support, like me. I found some good pointers in there.
Micah Dubinko also has an article on XML.com, discussing
Ten XForms Engines. I'd really like to see a Firebird plugin for this. And one that could generate a SVG / Flash .swf file given an XForms document.
From XMLhack, comes news of James Clark's GNU Emacs mode for XML
nXML. nXML can do validation based on Relax NG schemas.