Jon, the context bar has improved over the last few years. I just fixed up one package which used the old ad_context_bar procedure on each tcl page and then the @context_bar@ variable on the adp page. The changes were:
Tcl page, just:
set title "My page"
set context [list "$title"]
...
on the adp page:
<property name="title">@title@</property>
<property name="context">@context@</property>
What shows up is a breadcrumb. I haven't looked into the assumptions made, I guess it just hopes you have index pages up to the main site.
