Microsoft Research has buit a new system for creating and experiencing "Rich Interactive Narrative," built on top of their Silverlight browser plugin. The system aims to provide a richer multimedia experience, allowing for both a reading and authoring environment.
So far, most of the examples are enhanced video experiences. They seem to offer video with deep-level zooming and annotation. I didn’t find these particularly deeply engaging from a narrative perspective, but can easily envision future works with more diegetic complexity.