I haven't been following this thread because of mail overload, so
forgive me if I'm repeating films that have already been named :
Play it Again Sam (watching from audience)
Desperately Seeking Susan (projection booth)
The Way We Were (private screening)
Sliver (voyeuristic viewing -- but on tv monitors)
Singin' in the Rain (watching from the audience)
True Romance, which has already been named, has both watching from the
audience and private screening.