www.aharef.info/2006/05/websites_as_graphs.htm

This processing based applet visualizes the HTML DOM structure of any website, with different coloured nodes representing different HTML tags.

http://www.aharef.info/2006/05/websites_as_graphs.htm

You can see loads of the generated visualizations at Flickr.

www.sferyx.com/htmleditorapplet/

An HTML editor applet, the JSyndrome applet is a full WYSIWG HTML editor that provides sophisticated editing and previewing of HTML documents and integrates with websites and Content Management Systems.

www.sferyx.com/htmleditorapplet/