Animated Film Encyclopedia. (Ref 791.433 W382) Jefferson, NC: McFarland, 2000.
Encyclopedia of Film Themes, Settings, and Series. (Ref 791.43 Ar58) Jefferson, NC: McFarland, 2001.
Film Encyclopedia. (Ref 791.43 K159b) New York: HarperCollins, 1998.
Focal Encyclopedia of Film & Television Techniques. (Ref 791.403 F681) London: Focal, 1969.
History of the American Cinema (a 10 volume work)
International Dictionary of Film and Filmmakers
Schirmer Encyclopedia of Film
Videohound's Golden Movie Retriever
Mass Media — A Chronological Encyclopedia of Television, Radio, Motion Pictures, Magazines, Newspapers, and Books in the United States. (Ref 302.234 H869) New York: Garland, 1987.
World Encyclopedia of the Film. (Ref 791.43 C317) New York: Galahad, 1972.
Internet Movie Database - filmography and information about actors, directors, screenwriters, and others involved in cinema production. Be aware: now that it's owned by Amazon.com, the reviews seem to have been replaced by "viewer ratings" which almost always encourage buying the video rather than giving informed comments.
Pacific Film Archive in Berkeley is "an internationally recognized center for the exhibition and study of cinema." This site offers notes about each film being screened.
ScreenSite - for the study of film and television. All kinds of stuff including Monty Python scripts and Seinfeld transcripts as well as links to U.S. broadcast and cable networks, and TV from other countries as well.
And, of course, YouTube.