Zope + Formulator is a nice combination to validating and designing forms and add some functionality. If you want a more complicated content management framework, then you can additionally install plain CMF or Plone, which is based on CMF. There is also something called Silva, but it doesn't have many products as the other two; however, it is also nice.
I have heard also about CherryPy, Quixote, Twisted Matrix and Webware, but I haven't tested them. Once I saw that somebody posted a link, which compares some of them, but I lost that thread :-(
I found it: http://www.cmsmatrix.org/ -- http://mail.python.org/mailman/listinfo/python-list
