During the MacWorld Expo, Apple announced their new iTunes movie rental service in which you could rent movies from the iTunes store, your Apple TV set-top box, iPhone or other devices. According to MacWorld, Apple has fallen far short of that goal.
As of February 29, there were just 378 titles available on the iTunes online store, and only 351 titles available on the Apple TV unit. When you combine movies for sale and rental on the iTunes store, 770 titles are available.
Apple also announced at MacWorld that they will have 100 titles available in high-def, and it appears they are closer to that promise, though. There are currently 91 high-definition titles available to rent, although the site noted that not all of said titles are available in 5.1 Dolby Digital Surround Sound.