Finally started the iOS5 by tutorials book from the great collection of teachers on http://www.raywenderlich.com/
There are many chapters and I've been wanting to do something with a Calendar so I've jumped straight to there.
This chapter is by Marin Todorov http://www.touch-code-magazine.com/ who has made some excellent tutorials, many on RW and he also has a great course on Udemy.
Edit: Finished the Calander Chapter. Can add events to a custom calendar just for this app or add to existing calendars. This will be very useful for an app I've been thinking about making. Would like to add a calendar control to the app, and other things. Should be a good start for this though.
Next: AddressBook API, works well, nice and easy to do, when you link with the actual AddressBook library, d'oh!