Here are some examples of reliable websites:
Internet History SourcebookS Project: Modern History http://www.fordham.edu/Halsall/index.asp
"The Internet History Sourcebooks Project is a collection of public domain and copy-permitted historical texts presented cleanly (without advertising or excessive layout) for educational use."
There are entries under many of the people on your list. If you call up the name of the peron you are researching, one of the the top 5-10 entries will probably lead to to this site i.e.' Peter the Great and the Rise of Russia.'
http://www.britannia.com/history/monarchs/mon51.html for article on Mary Stuart
Use the search bar on the left - use for Diderot, Voltaire, etc.