Context: I have a D7 site using a standard embedded sign-up form for mailchimp. I just recently switched the site to https, which unfortunately causes some browsers (e.g. firefox) to throw a scary message when a user clicks the submit button on the sign-up form, because standard mailchimp embedded forms can only use http.
The mailchimp module uses the mailchimp API, which allows secure connections, so that's the obvious solution. And the mailchimp module automatically provides a block for each list. But the module makes assumptions that I don't want. So, instead of the automatic block provided by the mailchimp module, I'd like to create my own block(s) with a sign-up form that uses the api, so that I have more control over the look and feel of the form.