Jesus Franco was a 2nd unit director for Orson Welles on Chimes at Midnight and Don Quixote. It was his Count Dracula that forms the basis of Pere Portabella's Cuadecuc, vampir.
Ruggero Deodato, director of Cannibal Holocaust, got his start as second unit director on Rosselini's Il Generale della Rovere.*
This is on top of Roger Corman's record for starting such luminaries as Monte Hellman, John Sayles, and Robert Towne, on top of Coppola and Scorcese, of course.
The cross-pollination between auteurist sensibility in the approved and the shadow auteurs that exist in the netherworld of exploitation film deserves greater examination.
Jesus Franco is no Orson Welles, it's true. But just as Cahiers du Cinema rehabilitated Samuel Fuller, Edgar Ulmer and Howard Hawks for the art-house, our generation has to grapple with the disconnect between exploitation/genre and art-house. Some art-house filmmakers are breaking down the boundaries of their own accord. But we don't have any kind of discussion between these two worlds except in the practical terms.
In addition to the economic reasons, Hollywood and whatever metonymy would represent the independent film-world need to face the artistic legacy of these overlapping, cross-breeding worlds just because of the artistic options they suggest. This examination offers something beyond blockbusters and middle-brow.
*Cannibal Holocaust might deserve some sort of comparison to the goals and practices of neo-realism. It is grappling with the social systems that hold together society, looking at media's methods of manipulation of reality. The hypocrisy or effectiveness of the approach also deserve discussion, but blanket dismissal is way too easy.