You can find the slides of the entity API session "Drupal 7 development done right: Leverage entities!" from the developer days brussels 2011 attached to this post.
I've also attached them to session page of the dev-days site.
Entifying external data
It was a great session and since Brussels I look from a completely different angle towards Drupal 7. The ability of entities to store data in an external data source even provides a solution for my first ever question at drupal.org (#339414).
To bad there is not a great deal of documentation and examples available yet. I'd love to see an example of how to manage data in an external datasource by using Drupal and the Entity API. Would you happen to know any example modules or other code or something about that?
I'm sry, I fear there is no
I'm sry, I fear there is no good example for this yet. I've written a prototype some months ago though, which integrates entities of a remote Drupal system for use with Rules. You can find its code here: https://github.com/fago/rules_web (rules_web_remote)