GrumpyToaster

This plugin creates a simple contact form with a check box to subscribe to a mailman mailing list. The config is in the main file. Future versions will include the settings directly in the WordPress admin.

Contact Form with Mailman

Creates a simple contact form with a check box to subscribe to a mailman mailing list.

heikoch

The plugin creates a txt file where the E-mail addresses are stored in the associated widget form in the uploads folder of WordPress. 
This txt file can then be used to write to the interested parties through a cron job on the mailing list.

Mailman Registration

This plugin allows prospective customers to register on to a Mailman list.

Contact Form with Mailman vs Mailman Registration