The Official Academy Awards Database (updated through the 2008 Academy Awards) is a very helpful online resource. You are able to search by film title, nominee, and song title. You can also choose to Browse Statistics and check out lists that include "Oldest/Youngest Acting Nominees" and "Winners or Films Winning Both Best Actor and Best Actress."
Nominee Search: marlon brando
Results: Brando was nominated for 8 Oscars; he won two (Best Actor in 1954 for On the Waterfront and Best Actor in 1972 for The Godfather):