I've posted the notes from this morning's Processing XML with SAX and DOM tutorial at Software Development 2004 West.
JAPISoft has released EditiX 1.2, a $39 payware XML editor written in Java. Features include XPath location and syntax error detection, context sensitive popups based on DTD, W3C XML Schema Language, and RelaxNG schemas, and XSLT and XSL-FO previews. Version 1.2 adds a multiple view XSLT editor, SVG preview, generation of temporary schemas for document completion, and a DTD syntax checker. EditiX is available for Mac OS X, Linux, and Windows.