There is a growing trend for more and more music publishers to come out with piano PDFs and other forms of piano ebooks. I think it is a good development, because it does away with the delay between wanting to learn some aspect of piano playing and the fulfillment of that desire. With a physical piano course there is often a time gap of a week or more before the course reaches the individual buying it because of shipping time. But with a downloadable piano course a person can decide they need to learn that particular thing, and 60 seconds or so later actually be learning it!
Of course downloadable piano courses are much shorter in length than DVD piano courses and cannot by their very nature show full-motion video. But even that will change someday not too far off.
Here are a few PDF piano courses a person could download and start learning immediately:
"Become a Musical Mindreader"
"Power Piano Chords"
"Instant Chord Finder Software"
"Piano Tabs & Guitar Tabs"