[Mailman-Users] mailman plugin support?

[Scott R. Godin]

Is there any sort of plugin support possible for mailman?

I have an interesting scenario where the end-user wants to be able to
subscribe users to a sort of mailing list, where once a week for birthdays
and anniversaries, a cron-job generates a list of people who are due the
week following, and either prints (for snail mail) or e-mails them a
coupon.

Obviously their database will contain more info than name, password, and
e-mail. 

I'm pondering some sort of man-in-the-middle approach that captures the form
input from the web, and passes the appropriate details to mailman, but it
would be nice if there were an easier way to more tightly integrate it with
the list manager rather than merely using mailman as an ancillary, although
I'm not 100% certain of how appropos it would be. 

Any insights would be appreciated.