There are two Black Actresses nominated this year:
Taraji P. Henson for The Curious Case of Benjamin Button
Here is a the list for All Black Nominees in the Academy's History.
Winner Acceptance Speeches:
Hattie McDaniel, Best Supporting Actress - 1939, Gone With The Wind
Sidney Poitier, Best Actor- 1963, Lilies of the Field
Cuba Gooding, Jr., Best Supporting Actor - 1996, Jerry Maguire
Denzel Washington, Best Actor - 2001, Training Day
Halle Berry, Best Actress- 2001, Monster's Ball
Sidney Poitier Accepting an Honorary Oscar - 2001
Jamie Foxx, Best Actor - 2004, Ray
Morgan Freeman, Best Supporting Actor - 2004, Million Dollar Baby
Forest Whitaker, Best Actor -2006, Last King of Scotland
Jennifer Hudson, Best Supporting Actress- 2006, Dreamgirls
Could not find videos for the Best Supporting Actor Wins of Louis Gossett, Jr - 1982, An Officer and a Gentleman and Denzel Washington - 1989, Glory or Whoopi Goldberg, Best Supporting Actress - 1990, Ghost.