A Good Place to Start, http://www.classicfilm.about.com/entertainment/classicfilm, An essay on the history of classic film, this is a good place to start finding ideas.
The Bill Douglas Centre for the History of Cinema and Popular Culture, http://www.ex.ac.uk/bill.douglas/index.html, A good compilation of information on the history of film.
Lecture Series, http://www.gen.umn.edu/faculty-staff/yahnke/film/cinema1.htm, A compilation of lectures on the history of film by era.
30s Movies History, http://www.geocities.com/Hollywood/Lot/4344/index.html, Another good place to start, this site provides fabulous background on the history of 30s movies.