TV land has put approximately 1000 movie trailers on their website, and you can search alphabetically, by decade or by genre.
Would you like to hear Brando scream STELLA! in A Streetcar Named Desire? How about seeing James Dean in Rebel Without a Cause. How 'bout a trip through the 80's? You can check out Empire Strikes Back, or would you prefer Caddyshack instead?
It is weird to see trailers from different decades. The ones from the '50s almost seem like they're mocking themselves - brings to mind Mystery Science Theater 2000. There is a weird 80s' sitcom soundtrack behind The Princess Bride's movie trailer that makes it seem cheap and cheesy. The deep-voiced narrator we know from today's movie previews shows up somewhere in the late 80's/early 90's, and the trailers seem a little more well produced.
Check them out.