The Center for Media Integrity has a really cool website in which you can find out who owns the media in a particular area using zip codes as a search term. You can see how this works by clicking on the link for the search page for the 44256 zip code by clicking on the link in this entry's title. The map that the site uses is interactive and you can find out ownership for both cable and broadband television stations, radio stations, and newspapers. The map allows you to change the area that you are looking at and to zoom in and out to make the area bigger and smaller.
The site tells you who owns what and links to websites of the owning companies. It is good to know which company owns what in the event you are organizing campaigns to pressure advertisers, or you want to know where to send complaints or inquiries.