I wrote an XSLT stylesheet that would turn any page into a pretty-printed source view of the HTML just by including it via the <?xml-stylesheet?> tag. That was during the years I worked at a publishing company that stored, generated and edited everything via a combination of XML, XSLT, XPath, XInclude and XQuery, and now I'm working somewhere else that generates documents I do miss the flexibility of that combination... unfortunately it's hard to sell anything XML-related to people who've never seen it used effectively.