Here are a few that are worth looking at.
1. www. archive.org. This is the 'Internet Archive' site and is the best of those I've seen. By clicking on the relevant categories, you can find some real classics.
The Film Noir and Sci/Horror sections are particularly good. Shadow of a Doubt, Detour, House on Haunted Hill are there, also Mickey Rooney in Quicksand, plus many others. Some play in Windows Media Player (mpeg1 seemed to open this) or just click the arrow in the screen.
A long list of classic tv is there, including One Step Beyond and Quatermass 2 (original tv broadcasts).
2. emol.org/movies. This is the Entertainment Magazine online site. There are Crime/Mystery and Horror/Sci-Fi categories, with films including The Man Who Knew Too Much (Hitchcock's 1934 version) and Lang's Scarlet Street.
3. freemoviesonline.com. The Horror section includes Edgar Ulmer's Bluebeard, White Zombie and numerous others in various categories such as Drama, Horror, Mystery, Sci-Fi.
4. movieflix.com. Although plenty is on offer, you have to register to view and only a selection are free.
As you'd expect, the quality can be a bit dodgy. Sometimes the film wouldn't play, other times the picture would freeze or shake, but then they are free. As a novice to this, I don't know whether this down to the type of streaming or limitations of my system.
There are plenty of surprises. On the same site you have Ida Lupino's The Bigamist and The Stranger (Orson Welles) along with cheapo sci-fi flicks (freemovies).
So if your television, dvd or video player breaks down, just log in and watch.