I checked out Vudu's website tonight, and found that they offer a TON of Disney movies for rent and/or to own via digital download, both plenty of new popular titles and a lot of wonderful old classics, both animated and live action, including some rare titles.
VUDU - Watch Movies
You can see trailers for some titles, and most have two-minute previews to watch the first couple minutes of the movie. I was pleasantly surprised by one title in particular, 1961's Moon Pilot. The image and sound quality are both outstanding on it. I was also pleased to see that there are a few True Life Adventure titles, as well as most of the Disneynature titles. I like that one of the options, for many titles (but not all) is to choose the image quality for the digital downloads - either SD (480p), HD (720p) or HDX (1080p). Some titles, however, are only available in SD format. They still look pretty good, though!