One of the things I've been enjoying on my new iPad is the Guardian app, which I think I can now say I find both easier and more enjoyable to read than the print edition of the newspaper. It's easier to handle, of course, being smaller, but I also find that I browse more and find myself reading more items than I used to do. (I don't use it at the breakfast table though, to avoid marmalade on the screen.)
But the improved readability and usability is down to some great information design, not solely the change of medium. Each issue is clearly divided into sections, and it's easy to switch between them or pop up to the whole-issue level. Within each section, the items are presented to you with a headline, a standfirst, and often a photograph. The photographs are strong, and look really striking on the iPad's retina display, and provide fixation points for each item. But what is more critical in determining whether or not you tap on one of these to read it is the quality of the standfirsts: those short paragraphs before the article proper, which both explain what the article is about and give you a reason to read it (as explained here and here).
Now all of these elements - sections, signature photographs, headlines and standfirsts - are features of the print edition also. They are part of the standard information design repertoire of journalism, and their quality is probably the most critical contribution to the usability of the iPad edition. In a sense all that's needed for the iPad edition is for these to be put on the screen appropriately - not a trivial design task, and one which they could easily get wrong, but one which is made considerably easier by those elements existing in the first place.
To write online learning materials as compellingly and addictively browseable as the iPad edition of the Guardian we may need to adopt some of the same techniques, to focus on that same point in time when a reader is scanning the screen and wondering what to do next. Pictures need to be interesting and relevant, titles need to be meaningful, and any introductory matters equivalent to a standfirst needs to sell the item not merely describe it, because it exists in competition with all the other things the reader or learner might be doing instead. We don't need to be apologetic about this; if we have materials which are good and interesting we shouldn't feel embarrassed about promoting them.