Snappy includes a Campaign Monitor App that will allow you to subscribe contacts into a list you specify.
You can set this up inside the "Apps" section of Snappy. Here is the setup form:
After it's setup any time a new contact is created they are automatically pushed into your Campaign Monitor list.
This can be useful in a variety of situations and one of the most common use cases is for teams to email customer service surveys. By having all the contacts in a list you get all the tools Campaign Monitor offers including scheduling, A/B testing, and hundreds more.