The Virtual Business Library (VBL) is a very useful tool for identifying resources in specific categories, including industry research, marketing research, company and financial information, etc. It includes links and descriptions for specialized business resources, journal and periodical databases, research guides, and a searchable FAQ.
Use these sources to learn basic information about a media company. Note that more information will be available for publicly traded companies.
To understand more about a specific media industry, try these sources.