Scott Gamon

signup-page is a plugin that allows you to create a public signup page. A signup page is just a list of stuff 
that you can sign up for, with a space next to each item where someone can sign up.
There is no validation of input, and no login is required. This is a true public signup page. However, when a 
person signs up, that slot is frozen to the public (no further changes). Site admins can make changes to any slot, 
at any time.

Signup Page

Creates a public signup form where people can sign up for pot lucks, volunteer jobs, whatever.

wp.insider

smp7

This addon allows you to specify a MailChimp list name for each of your access levels. When members join your site, they get signed up to the specified MailChimp list.
This addon requires the <a href="https://wordpress.org/plugins/simple-membership/" rel="ugc">simple membership plugin</a>.
After you install this addon, edit your membership level and specify the mailchimp list name. Then go to the MailChimp settings interface and specify your API Key.
Read the following page for step by step usage documentation: 
https://simple-membership-plugin.com/signup-members-mailchimp-list/

Simple Membership MailChimp Integration

An addon for the simple membership plugin to signup members to your MailChimp list

Signup Page vs Simple Membership MailChimp Integration