The following multi-subject databases cover a wide variety of subjects and are a good place to start looking for discussions of historical topics, including events surrounding the World Wars.
These specialized databases focus on more specific subject areas. They are good for finding treatment of specific topics related to the World Wars and analysis of those issues from the perspective of disciplines such as economics and political science.
Below are a few selected resources on World War II and the Great Depression. These are useful for overview and background information on a specific subject or topic.