If the question here is How to learn Backbone, my suggestion would be to take one of the to-do app examples and just build and hack on that until you develop the app you want. Try doing it with just built-in backbone functionality; don't override any of the defaults. Use hacking an already built-app to get a feel for the limitations of the framework, which in turn will show you some interesting (for me, at least, coming from MVC world) design patterns.

If the question here is Where is a good Backbone tutorial, I encourage you to look at the tutorial on Backbone-Relational (which is a plugin for Backbone):

http://antoviaque.org/docs/tutorials/backbone-relational-tut...