One very easy way to start your research is to look in an encyclopedia that will provide an overview of basic background information on a topic. For example, Wikipedia is an excellent place to get background information. See the WIKIPEDIA guide of more.
eLibrary is an online database paid for by the Library, contains several encyclopedias and almanacs in its Reference section.
Vogue Archive is a resource is perfect for historical research because it has every issue completely available going back to the late 1800s, including ads, articles, etc. All searchable by key word and date range.
There are books which you can browse which will be extremely helpful to you in learning about the cultural, social, and historical context of a particular time or period.
Modern Art Movements: 1870s to 1980s: Displays major trends and movements in modern art.
Year by Year 1900-2001: This site describes historic events of the twentieth century by year and by decade.
Heilbrunn Timeline of Art History: Pairs essays and works of art with chronologies, telling the story of art and global culture.