Since October 2005, Apple has collected and offered movie trailers for people to watch through iTunes.
Movie trailers have been a mainstay on Apple's website, as well as Apple's mobile devices and the Apple TV, since then.
For the release of the new Apple TV, which just arrived last week, Apple completely redesigned its movie trailers app to be much more useful. And I love it.
(Pardon the photo quality, I don't have the proper hardware to take screenshots on this Apple TV just yet!)