Finding a Epub3 demo used to be rather difficult, and I can recall the digging I had to go through when I wanted to see one for the first time. Luckily for eBook geeks, that is about to change.
The IDPF recently started a new project which is going to make it easier to keep up with the latest Epub features. Rather than ask around for people to point you at sample files, you can now check one single site where (I hope) you’ll be able to find all the demos that the various developers have been working on.
As of this week, there were 8 files on hand (I’m hoping that will increase). Right now you can read them in iBooks, and they show off various tricks like embedded fonts, video, and audio.