It is really quite easy to use the built in (Zope) function VHM - Virtual Host Monster - to set up a vanilla (windows, using standard plone installer) installation to serve out different sites. There is one trick that might drive you mad before you know it.

This applies only if:

• you're using Windows
• you're not using Apache or some other front-end webserver

So:

• Install Plone if you havent already
• Add and set up plone site from the ZMI (you use the drop down from the root)
• Add a VHM in the ZMI root, using the add dropdown. Must be in the root. Name does not matter.
• Click the new VHM node in the root that you just created, read instructions on the first tab. Re-read until you go nuts. Then choose the other (mappings) and enter the mappings: Really, if you have a domain mydomain.com and you created a Plone site in the ZMI root with the name mydomain you need to put an entry mydomain.com/mydomain. If you want to have it answer to www. you also need an entry for that (ie www.mydomain.com/mydomain).
• Here is the trick: We are NOT done! Save the mappings and then go to the plone installation catalog on your harddrive, into the directory Plone 2\Data\Products\CMFPlone\Extensions. There you will find a file accessRule.py with some instructions. Follow them or do what i did, replace the last three lines with some null statement (like pass):

    def accessRule(self, *args):
        pass
  

• Restart Zope from the ZMI control panel and everything should work.