Signup forms - additional list choice

Signup forms - additional list choice

  1. We want to provide leads/prospects an option to select public lists for subscription. It seems like by default we can configure a signup form to add the lead to multiple lists - we want the user to be able to select which public lists to subscribe.
  2. How can we have a web page where the user can update the subscriptions - subscribe and/or remove themselves to additional public lists.

Thanks for your help.