I’ve made this introductory topic a Wiki, so if you are level 2 user, you will be able to edit it.
Here are a couple older examples which might be useful:
https://github.com/themorgantown/iBook-widgets. This includes some tricks with localstorage, audio & video, and an embedded spreadsheet demo.
I think for purely educational examples, it would be useful to start a new thread onto which we can share an updated set of widget examples – the idea being to keep the practical & technical widget tips separate from the functional / education examples. Could I share the few widgets that you already shared with me as a starting point?