Here are a few movies about movies that I can think of (sorry
the info. is not more complete):
 
S.O.B. (Blake Edwards)
The Player
Barton Fink
Singin' in the Rain (1952)
Holiday Inn (the last few scenes, anyway; 1942)
Hearts of Darkness (may not work, because its a documentary)
Silent Movie (Mel Brooks, 1976)
The Buster Keaton Story (this may not be the exact title; the
    one with Donald O'Connor)
Man with a Thousand Faces
Gable and Lombard
The Last Tycoon (1976)
Peeping Tom (cringe)
 
Also, there are a few movies that I don't quite have a clear
memory of (like the title): one with Steven Boyd about the
Oscars; one fairly recent one with Kevin Bacon (may have been
a direct-to-video release about Hollywood); and one from
the sixties where George Peppard plays a pseudo-Howard
Hughes type.
 
Hope this helps.
 
Matt McAllister, Virginia Tech.