Mailchimp iCal Link

To get your list URL:

Click on Lists > list > Sign-up forms

Click on your sign up form url to open it in a new window

The url will be something like this:

http://<ACCOUNT_NAME>.usX.list-manage.com/subscribe?u=<USER_ID>&id=<LIST_ID>

Get those details and add the following link calendar by URL

http://<ACCOUNT_NAME>.usX.list-manage.com/ical?u=<USER_ID>&id=<LIST_ID>