There are good and bad sources of information about the cinema. Many commercial or “fan” sites exist online which seem to have a lot of information, but may not be entirely accurate. It is always best to consult more than one source when doing research.
Books are still a valuable source, since they are detailed and typically the author and publishers have been very careful to fact-check everything. Champlain Library has an enormous film collection, with books on many topics. These will be available to you along with help from their very knowledgeable reference librarians. Contact the library to see if they have material on your particular subject.
As for online resources, Wikipedia and the Internet Movie Database (imdb) are both very useful sites for general information.
However, beware of “filmsite.org” run by Tim Dirks, and now part of AMC network. This site may be useful for pictures and lists of different kinds – it will tell you details like “all the musicals made in 1943”, for example – but it is filled with ads, many useless or trivial topics (“Best kissing scenes in cinema”), and worst of all, most of the written material is plagiarized. If you quote anything from this site you will be in danger of plagiarizing, since a lot of it is taken from other more reputable sources, without crediting the real author.
By contrast, check out “TSPDT,” a home-grown site from a couple of movie buffs in Adelaide, Australia, which is simply wonderful.
Below are some useful online sites which provide research materials, ideas, and more.