#1. Get a library card. Most libraries in larger metro areas have a subscription to Reference USA - and it's an online subscription, so you can search from the comfort of your own home.
#2. Do a search using Reference USA by using the SIC or NAICS code for your prospects. For example, the NAICS code for "Speciality Food Retailers" is 445200. So you put that in the search form, and you can define/refine your search area by a whole bunch of different criteria (i.e. - zipcodes, cities, states, metro area...and the list goes on).
#3. The only draw back is while it will show you all the results, it will only allow you to download 10 results at a time, so you could be there all day.
Salesgenie.com will give you 100 leads for free too.
Once you get really large and make some good $$$$ you can use databases such as Hoover's or OneSource.