I've noticed a lot of people use google voice, for the hobby # and because of texts. Texts go to email, email goes to text. I think it is one of the more popular apps.
I've been using one again lately, mostly because it's harder to stay discrete while carrying around a separate phone. I've been using Hushed app with mixed results. It does let you create and destroy phone numbers in any area code in the app for a few bucks. But it also has issues with dropping long messages and sometimes not connecting phone calls properly.