After a little more reading I found a page on the Turbogears site itself about this subject too: http://docs.turbogears.org/1.0/BreadCrumb
The really interesting morsel though was the discovery of the cherrypy._cputil.get_object_trail() function that's part of CherryPy (itself a part of Turbogears). This basically gives you access to the path of objects CherryPy followed to invoke the current handler. Which basically means you can easily figure out the hierarchy of the url and generate a nice location based bread crumb trail.
So I've now added simple bread crumb navigation to chrss (my chess by rss site). That should go live in the next few days. I'll need to tweak it a bit though, as I'm actually subverting CherryPy in a few places, but it's a nice addition as it stands.