There's a lot to tell about Plone.
"Plone is a ready-to-run ["content management system"] that is built on the powerful and free ["Zope"] ["application server"]." So says the "[http://plone.org/about/plone/ What is Plone?]" page of the [http://plone.org Plone Web site]. Wikipedia also [http://en.wikipedia.org/wiki/Plone_(content_management_system) has plenty to say].
[Explain what this means.]
Plone.org maintains Wikis, but apparently only to process fault Tickets, that is, as a "[http://dev.plone.org/plone/wiki/ bug and feature tracker]". There's nothing directly comparable to the Python Wiki.
A PloneSprint is frequently scheduled--half-a-dozen times annually? There are local user group meetings, annual conferences, ...
Plone is particularly prominent in Latin America, Europe, ...