Check out Inanimate Alice. It's a spooky ongoing digital story conceived and published for the web, and it will suck you right into its tale about a girl whose father's shadowy work takes the family around the globe. There's an interview with the author in The Guardian. I was reminded of William Gibson's great Pattern Recognition, in which the heroine spends her spare time (and increasingly becomes consumed with) questing for "the footage," mysterious segments of film that show up in odd places and at odd moments on the internet.
For some smart thinking about how digital picture books might work read Jean Gralley's "Books Unbound."