It is interesting to look at the usage statistics at PyPI: [http://pypi.python.org/webstats/usage_200805.html#DAYSTATS]
Besides the front page, the most visited pages are in order (same thing
- zc.buildout - setuptools - zc.recipe.egg - plone.recipe.zope2instance - plone.recipe.distros - python-openid - elementtree - plone.recipe.zope2install
Then the packages in the top 60 are mainly zope eggs. This corresponds to the sequence done by a Plone or Zope being build in a buildout.
If you take a closer look at [http://pypi.python.org/webstats/url_200804.html], the next top hits corresponds to zope.* then plone.* packages.