Is there an elegant way (without hacking the plugin's code) to integrate a Contact Form 7 contact form to Mailchimp, so I can have a checkbox that when selected would register the email to a Mailchimp list?
This is what finally worked for me. The code needs to be updated tho. I don't have time now to get back to the refactored code but if someone requests it I will do it in due time.
This might work for you...
You'll still possibly have to modify the contact form's files but only to do this:
"You can manually place the checkbox by calling inside the form tags of your comment form."