>
> > Has anyone written a robot which maintains a cross-reference of which pages
> > link to which other ones? Better yet, are there any search engines which
> > will allow searches by link other than AltaVista?
>
> There is a tool named Web Core that displays the reverse links for a
> given url.
>
[...]
Also in this vein, although not a robot, there is my RefStats script
which can analyse a referer log to detect links to a server if you
have access to the log files.
<URL:http://www.netimages.com/~snowhare/utilities/>
-- Benjamin Franz