ascii: ASCII XML Tree Viewer produces a plain text document that shows, in the form of 'ASCII art', the node structure of an XML document.

html: Pretty XML Tree Viewer produces an HTML document that shows, in the form of 'ASCII art', the node structure of an XML document. A CSS 1 stylesheet (tree-view.css) helps render the HTML in an appealing style. I highly recommend trying this one.

Both of these stylesheets were featured in the 2004 O'Reilly book XML Hacks (ISBN 0596007116). They're "hack" number 34.