By Jeff Davis
</authorblurb>An alternative to psgml mode is nXML by James Clark, a new major mode for GNU Emacs for editing XML, and which features highlighting, indentation, and on the fly validation versus a RelaxNG Schema.
An introduction to nXML mode at xmlhack.com.
The nXML mode mail list at groups.yahoo.com.
The nXML download page at thaiopensource.com.