It's always a good idea when you go to write cover letters and go to interviews to have some idea about what a company does, how large it is, what some of their goals are, and how well the industry or field they are in is doing. This is called company intelligence.
There are a number of news sources and business databases that have company information.
Generally, if a company sells stock (called a "public" company), it is easier to find out about it because they have to file reports with shareholders and with the government.
Private companies are much harder to find out about because they are not required by law to report anything more than taxable revenue. Sometimes, news stories are helpful, if there are any.
Delaware Valley News Sources
Big Company Sources - Articles, Overviews, Industry Overviews
Wall Street Journal Full-Text (1984 - present) [via ABI/INFORM Complete]
Mintel Market Research Reports