Now I haven't yet gone through the Imdb top 250 movies, so imagine my despair reading the Observer this week end: they have a list of "50 Lost Movie Classics". All I need!
Forgotten films from the 30s, first features, weird ones ("Le Petomane", by Ian MacNaughton, about a man with an elastic anus)... there's even a movie starring Kevin Costner (Tin Cup)!!
Definitely an interesting list.
And if you feel that a movie is missing, they've opened a page on their blog for your suggestions.