I've made a Plone 3 buildout to get people up and running with reliable versions of PleiadesGeocoder, SpatialIndex, and all their dependencies. You can get it from our repository, build it up, and start it like so:
$ svn co http://svn.gispython.org/svn/zope/geo-products-example/trunk pgx $ cd pgx $ python bootstrap.py $ ./bin/buildout -v $ ./bin/instance start
Create a Plone site through the ZMI, install the PleiadesGeocoder and SpatialIndex products through the Plone control panel, and you're all set to geocode and spatially index content. Unfortunately, it's not going to work on Windows. I haven't even started looking into how to build GEOS or the spatialindex lib on win32.