UserLand's XML apps are here:$598 (Discussion group in XML)$281 (Folder traversal in XML)

All of these applications are dynamic, meaning that they change. The
Scripting News XML file changes whenever the HTML version changes, for
siteChanges, it's rebuilt every night at midnite to reflect changed files
on the server, and the Discussion Group and Folder Traversal apps are
real-time, the XML is computed on the fly on the server, when messages or
files are added or modified.

Some of these are now advancing past the stage of just being demos and
proof of concept. A search engine company is working on supporting the
database side of siteChanges.xml. And we're building workstation software
that plugs into the messaging system, using XML as the transport format. A
Shockwave client is being built for the discussion group (Director 7 has a
builtin XML parser).

Dave Winer
UserLand Software