Holy crap, The Third Man's up for free?!! The Thirrd Man is just fiercely, relentlessly brilliant. It's not horror but it's a magnificent film, a character study of broken people in a broken city where every map from the geographical down to the moral is being redrawn. Also, the speech on the Ferris Wheel is one of those moments where you just go 'Oh, THAT's what cinema is for.'
As an aside, for me, at least, the closing scene of Clerks 2, set to 'Frustrated Incorporated' by Soul Asylum is another:)
M I've never seen but there's a stunning radio version (Starring, amongst others, Kevin 'Lucius Vorenus' Mckidd) that I've been listening to pretty constantly for months. It's a horrible, horrible story, filled with moral ambiguity and the abject terror that comes from mistaken perceptions. It's DEFINITELY horror and if the radio version is a diluted adaptation? Then the film should be amazing.