These days it is quite easy to find out quite a bit of information about companies you are interested in. The inter-net is a quick and easy place to start your investigation. The library is also a great place to round out your search. Be careful however.
Surveys indicate that knowing about the company is in the top ten reasons why a candidate is hired.
But knowing about the company is in the top ten reasons given by employers for not hiring a candidate. The trick is to know about the company but not to act like you have been investigating the organization. Quoting facts about the company to your interviewer is not advised.