I want to have a newsletter signup form that has a dropdown field that a non-signed in user can select from. I want their selection to assign them to a smart group for later use in bulk mailings. What's the best way to accomplish this?
Jsgoti, Welcome to CiviCRM SE. You definitely achieve this using Caldera module. All you have to do is
1 - Create a form with First Name, Last Name and Email field and also drop down in Caldera form.
2 - Click on Processor tab.
3 - Add a new processor of type 'CiviCRM Group'.