To learn iOS development, I took the Big Nerd Ranch Beginning iOS (iPhone/iPad) class. It consisted of almsot 7 days of full-time instruction. 2 days of Objective-C, followed by 4 1/2 days of iOS.
The class was held at an epic lodge an hour away from Atlanta, GA. The location was great, because it allowed for uninterrupted learning. Food and lodging were included in the price.
I highly recommend the course. If you can’t afford it, or can’t take a week off from whatever you’re doing, start by reading their books: