Saw your post regarding the UCMP website.  I think that part of the
answer is penetration and part of the answer is aggresive marketing and
the final part of the answer is breadth.

        The penetration aspect is potentially most interesting.  We are
linked by a lot of sites because we have been around for so damn long,
longer than any other museum web site by a good half year.  We have
continually developed the site too, so that the site does not look
old or out of date.  Much like a snowball, the longer a site is
in the public eye the more links that others build that brings other
web designers to the site and so on.  As long as the site retains
visual interest and quality, that snowball effect is hugely important.

        Aggresive marketing is just getting the URL's to the right
people and places.  We all do that as Web Admin's.  The breadth part
is important.  Lots of people link to "echinoderms" without ever
realizing the exhibit is part of the UCMP web site.  Some reviewers
have given us better marks on subsections of the server than the whole
server (the fools at POINT, who I am learning to despise --- see
http://ucmp1.berkeley.edu/reviews.html for a peek).

        That is my opinion about why we are linked by some many people,
besides the great job all the web designers do.

Cheers,
Rob