Fellini's '8½' is one of those film classics that are probably cited more than seen. Called "the definitive film about filmmaking" by Sight & Sound, it certainly godfathered a whole genre of ironic, self-reflexive, autobiographical films-about-films. In the case of '8½', even the title plays along, referring to the number of films Fellini had made at the time. ('The Beautiful Confusion' was a working title for the project.)
The story of '8½' is great: a successful film director (read: Fellini) is about to start production on a new film, the whole circus of cast and crew is already there, but he has writer's block and still no idea what it should be about. While he looks into his own life for inspiration, and reality and dream increasingly interweave, he is harrassed by producers, actresses and critics, to the point where he orders the only tangible set piece of the film (a giant space rocket in scaffolds) to be demolished...
Early on in the film, the director's script is criticized by a writer who says: "From the start, the action reveals a poverty of poetic inspiration" -- which is just the opposite of what you could say of '8½', especially after the memorable opening dream sequence (which, by the way, must have been an inspiration for R.E.M.'s 'Everybody Hurts' video).
More info: 'I, Fellini' - Fellini about making '8½'.