In 1999 I took over the running of an online community for business and personal coaches. Initially a simple email discussion list run on the Mailman open source software, once we hit 500+ members I decided to upgrade the systems.
At the time (about 2003) there was very little ready made community software available. So I created my own.
Mailman is written in Python. To migrate the data it seemed easiest to stick with Python, and I selected Zope as the web framework.
I extended the MailBoxer email distribution component and added digests (HTML, text, attachments). And I created the Zope website with a members-only message archive, online payment system, automatic subscription management, profiles and a classified adverts section.
The new system has been running for about 10 years now, seen many 1000s of members and 50,000+ messages.