Recommendations to replace Mailchimp

As some of you probably know, Mailchimp have brought in new t&c’s which make it a deal-breaker for some clients - anyone have any recommendations for replacements?

What would be good in an ideal world would be some possibility of integration with Freeform or, more realistically, available add-ons to allow subscribers to add themselves via the homepage.

Anyone got any (non-extortionately priced) suggestions?