Is your goal to ship apps or is your goal to learn Obj-C?

If your goal is to just ship apps, pick a framework or tool that lets you get your app out there as fast as possible - PhoneGap+Sencha Touch/Kendo Mobile for informational apps or something like Corona for games.

If your goal is to learn Obj-C and build apps using it, you should just pick a basic app like a todo list, twitter client, whatever... and just solve the problems one at a time until you have a working app.

Books and tutorials are fine, but they're also a great way to procrastinate building the app that you are trying to build. If you are trying to build something, just build it.