Benchmark Mail and MailChimp Joomla integrations are here!
You will ask: "Are there already integrations for those services? Those sounds as well known and popular services! There already have to be something." The answer is: "No". There is no integration like this.
This integration is Newsletter subscription during registration. After plugin setup, user will see checkbox on registration form.
The Joomla core registration form does not looks attractive in Joomla 3.3.1-dev. But you've got the point.
After registration, user email will be added to selected contact list of campaign on your Benchmark Mail or Mail Chimp servise. You can purchase those integrations here.
Note that we already have the same integration with Smart Responder. It is Russian by default but it has English language and is a cheapest service of this ikind ever.
And another one Getresponse integration on it's way.