Here's a few I found on a website...

Click on "Galleries". Click on "DVD Credits". Click "Next" on every page of the DVD credits section. This will lead to a clip from "The Sopranos" featuring an "advanced bootleg" of the "Godfather" DVD.

Click on "Setup". Once in the "Setup" menu, press left. A globe should now appear in the top right corner of the screen. Press enter to see a multi-language reel.

Click on "Behind the Scenes". Both menu pages of this section have audio of rehearsals playing over the menus.

Click on "The Family Tree". From there, click on "Santino (Sonny)". For the next menu, click on "Santino (Sonny)" again. Now click on James Caan's picture on the top of the page. Finally, click on James Caan's picture on the left of the page to view a clip from Caan's audition (featuring his impression of Brando).

Click on "Filmmakers". Click on "Mario Puzo". Press the left button twice. A green dollar symbol will appear over Puzo's biography. Press enter to find out why Puzo wrote "The Godfather."

Each of the biographies in the "Filmmakers" section has a shortcut to a relevant special feature from the "Behind the Scenes" section. To do this, go to one of the biographies in the section, highlight "Previous", and press left. The filmmaker's name will be highlighted in the top left corner of the screen. Press enter to see a special feature related to the filmmaker. (For example, the shortcut in Francis Ford Coppola's biography will lead to the "Notebook" featurette. Carmine Coppola's shortcut will lead to his featurette in the music section.)