Firefox and Iceweasel, when encountering a news feed, display a page that
allows the user to subscribe to the feed, using Live Bookmarks, Google Reader,
Bloglines, My Yahoo!, or an external reader program. The list of available
applications comes from URIs and titles in the preferences, under
browser.contentHandlers.types.*. For the benefit of people who use
aggregate as their feed reader, the ikiwiki CGI could expose a URI
to directly add a new feed to the aggregated list; this would allow users to
configure their browser to subscribe to feeds via aggregate running
on their site. We could then provide the manual configuration settings as a
tip, and perhaps provide an extension or other mechanism to set them
automatically. --JoshTriplett