Most of the links below are to the "biographical" section of general Black History Sites. You can move backwards in the sites to find more information on events and general historical facts.
Biography.com Celebrates Black History Month http://www.biography.com/blackhistory/
Encyclopaedia Britannica Guide to Black History http://blackhistory.eb.com/
Encyclopedia of Prominent African-American Leaders http://www.teachervision.com/lesson-plans/lesson-4429.html
Black History Month -- Biographies (Resources from the Gale Group) http://www.galegroup.com/free_resources/bhm/bio/index.htm
African-American Leaders http://www.kn.pacbell.com/wired/BHM/bh_hotlist.html#Leaders
Prominent African-Americans http://www.aawc.com/paa.html
Sports Illustrated for Kids Salutes Black athletes http://www.sikids.com/news/blackhistory/index.html
Black History - A wealth of links to people, places, events - notjust biographies. http://www.ecb.org/surf/blackhis.htm
Who's Alive and Who's Dead http://www.whosaliveandwhosdead.com/
Scholastic: Culture & Change - Evolution of Black History-Timeline http://teacher.scholastic.com/activities/bhistory/timeline/game.htm
Black History Hotlist http://www.kn.pacbell.com/wired/BHM/bh_hotlist.html
National Geographic Online presents : The Underground Railroad http://www.nationalgeographic.com/railroad/
Don't forget the school library ! Sources include encyclopedias (print and electronic), biographical dictionaries, biographies, specialized black history timeline books.