My friend SteveC told me about TK3 from Night Kitchen. He said this was one of the more interesting tools he has seen in a while. He said that TK4 will come out as open source and should be useful for education and those who share info online.
Nightkitchen says, TK3 is both a new format for multimedia electronic documents and a flexible, easy assembly tool for making them.
I've downloaded the reader, but not done much with it yet.