Stanford University publishes their iOS App Development lectures on iTunes U, for anyone to download. Both HD videos and lecture notes are available.
There is material available from older quarters if you want to go for Xcode 3 and iOS 4. New material from 2011 is also available, which includes iOS 5, Xcode 4, Storyboard, iCloud and other new features of iOS 5.
The instructor is Paul Hegarty. He explains very well and makes the videos enjoyable to watch. You will learn not only the technical part of iOS and Objective-C but also how to create user friendly apps, what to avoid and best practices. One of the best instructors you can get.
I've watched all videos from both quarters below and even if you've seen Fall 2010 I highly recommend Fall 2011 because there is plenty of new information about the new features of iOS 5.
For iOS 4, please look at: Fall 2010
For iOS 5, please look at: Fall 2011
If you're looking for a good book, I can recommend this one. It explains in detail how Objective-C works and will give you a good insight into the language. -Link to Amazon-