Because of the way the internet is set up - a web of interconnected information - much online art explores non-linear, associative means of expression. Which pushes quite a bit of it away from "storytelling" and into "explorational" or "conceptual" art. A veritable treasure trove of projects exist that are less about storytelling and more about re-imagining information systems, interaction or conceptual ideas.
Here are a few examples of more "storytelling" sorts of projects, some of them very hypertextual:
The broad term Digital Art can also mean (depending on your definition) things such as video and computer games. In this case, broad strokes can be made to incorporate games such as Myst that are, in essence, interactive storytelling.