Encyclopedias are a good place to start if you need an overview of a topic you are unfamiliar with. They will often include a bibliography of sources that you can consult for more information.
Marquis Who Who on the Web provides biographies of over 1.4 million people of note, in the United States and around the world. It is the online counterpart of Marquis renowned biographical dictionaries. All biographies since 1985 are included.
An illustrated collection of 60,000 biographies of men and women who shaped all aspects of Britain's history, up to the present.