I would really like to see ebook reader software for the N900 which would allow you to dynamically switch back and forth between text only and text-to-speech modes. The scenario I envision is reading at home as on-screen text and then continuing in audio mode while driving to work, etc...

In broader terms, I would love to see a mixed media file format that would mix professionally read (non computer synthesis) audiobooks synchronized to display of the underlying text. Something along the lines of "follow the bouncing ball" sing alongs. Such a format would allow one to enjoy content in whatever form is most convenient to the moment.

I can also see such a system being highly useful for those attempting to grow vocabulary and polish pronunciation in a foreign language. Some of the best casual speakers of English I've met (for whom English is not their native tongue) have been self-taught through watching movies.