I’m sure there are some of these around already, but I have written a script to back up your Mailman mailing lists. It dumps the member roster and list configuration into separate text files, zips them up, emails them to you, and cleans up after itself.
The script is called mailmanBackup.py, and its syntax is pretty straightforward:
Usage: mailmanBackup.py listname <recipient> [<sender>]
If sender is not specified, the recipient is used as the sender. The recipient can also be a comma-separated list of email addresses.
Typical use would be to place a helper script like this
/usr/local/bin/mailmanBackup.py listname email@example.com
mailmanBackup.py is available under a CreativeCommons-Attribution license.