MacTutor History of Mathematics: Roger Bacon  
   Concise biographical article, with links to articles on related thinkers.
   http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Bacon.html

Roger Bacon's Place in the History of Alchemy  
   Footnoted journal article by Edmund Brehm, discussing Bacon's contributions to alchemy. Features a diagram showing how alchemy fit into Bacon's world system.
   http://www.levity.com/alchemy/rbacon.html

Catholic Encyclopedia: Roger Bacon  
   1912 article by Theophilus Witzel, providing an extensive overview of Bacon's life and works.
   http://www.newadvent.org/cathen/13111b.htm

Memoirs of Popular Delusions: Roger Bacon  
   Excerpt from this work by Charles Mackay.
   http://www.worldwideschool.org/library/books/relg/socialeccltheology/MemoirsofPopularDelusionsV3/chap12.html

A Guide to Thirteenth Century Theologians: Roger Bacon  
   Dates, extant works, recent bibliography.
   http://home.sandiego.edu/~macy/Roger%20Bacon.html