You can find old movies for sale on Turner Classic Movies' official website, ShopTCM.com. The site frequently features a variety of discounted titles as well as the ability to search for a certain movie by actor or actress.
ShopTCM.com's Greatest Classic Films Collection is a series of movies sold in bulk categorized by actors, directors, fictional characters and genres. Among these box sets are movies starring Cary Grant, Gene Kelly, Judy Garland and the Marx Brothers. The collections are also comprised of films directed by Alfred Hitchcock and featuring the character of Charlie Chan, as well as Westerns, romantic comedies, murder mysteries and musicals.