Form to Mailchimp add-on for Google Forms integrates with Mailchimp, allowing you to create or update subscribers/contacts/members while your form is submitted.

Free Features/Limitations:
 * Create 25 contacts/month

Premium Features:
 * Create any number of contacts as per your Mailchimp plan

Video help: https://youtu.be/eefuOv9_OmA
For more details about quotas visit: https://developers.google.com/apps-script/guides/services/quotas