There are about 20 million Catholics in the United States who shop on the web. Even if you don't have a website (which you should), you can let Internet shoppers know about your local store.
The three most popular places to search are Google, Yahoo and MSN. All of these sites have local search features that allow people to find brick and mortar businesses.
Google Local lets you add your business to the directory for free. This directory lets people search by subject and location. For example, if I search for "Catholic" in "Colorado Springs", I get listings of the various Catholic churches and Catholic stores in Colorado Springs along with a map showing their locations.
Yahoo Local has a similar service to Google but allows you to upgrade to more prominent listings for relatively low fees of between $10 and $25 a month.
MSN Local, like the other services above, displays location information for your business but we have been unable to figure out how to edit or enhance the information provided. If anyone does know how, please comment below.
If you don't mind spending a little money to promote your business locally, you can use Google Adwords to only display ads to people who are in your city or even more specifically, people who are within a certain distance from your store. (I have no idea how they figure this out.)
Yahoo Search Marketing also offers a similar local search advertising option.