Zope and Plone
I had "played" with Zope years ago, but without the knowledge of Python I have now. I better understand why Frontier people that knew Python loved it so much back then... and it's definitely improved a great deal since I looked at it last.
One great thing is that there's a Plone.pkg.tar file you can download that will install Python 2.1, Zope, CMF and Plone for you without hassles. I had the system up and running very quickly.