Great Question. How much do you want to spend?
Are you looking for "Free Services"
Do you have a more specific criteria that "all businesses?"
What is the profile of the "ACTUAL IDEAL BUSINESS?"
I would start with a Search of google by Austin Zipcodes.
Online Yellow Pages
4Square Location API for Retail establishments
Facebook Locations also can be helpful
You could get a list of "registered businesses"
If you want "Registered Domains" you could take a look at this site.