Alan Gullette has a web site dedicated to Ambrose Bierce as the author of supernatural stories. Gullette authored an interesting biographical sketch of Bierce.
The Ambrose Bierce Appreciation Society has a great deal of information on Bierce, from writings and verse available online to biographical pieces on his life and death.
The Ambrose Bierce Site has the rest of the story. This site features original material such as plays and articles about Bierce, a Bierce chronology, works online and Bierce sites and scholarship. There's also a link to The Devil's Dictionary.
"Ambrose Gwinett Bierce." Encyclopedia of World Biography, 2nd ed. 17 Vols. Gale Research, 1998. Reproduced in Biography Resource Center. Farmington Hills, MI: The Gale Group. 2003. Document Number: K1631000672. This document is available online through the public library to individuals with library cards.
Biographies provides a different biographical view of Bierce and other essayists.
Contemporary Authors Online, Gale 2003
Wikipedia is the free encyclopedia and it has a page of information on Bierce, including links to historical events and people in Bierce's life.
Selected Books about Ambrose Bierce
Davidson, Cathy N., ed., Critical Essays on Ambrose Bierce. Boston, MA: G. K. Hall, 1982.
De Castro, Adolphe Danziger, Portrait of Ambrose Bierce. New York, NY: Beekman Publishers, 1974.
Morris, Roy, Ambrose Bierce: Alone in Bad Company. New York, NY: Crown Publishers, 1995.
O'Connor, Richard, Ambrose Bierce, A Biography. Boston, MA: Little, Brown, 1967.
Saunders, Richard, Ambrose Bierce: The Making of a Misanthrope. San Francisco, CA: Chronicle Books, 1985.