Just got my copy of iPhone App Development: The Missing Manual. Trying to wrap my mind around the Objective-C overview chapter today. I've had a class in Java, used to be able to make things happen with Actionscript, and now know some Processing, but Objective-C and the whole iPhone/iPad SDK are very different environments for me.
I'm going to keep working at this, but realize that it's not just going to click into place as a new way of thinking. If I can get through the overview chapters on Objective-C and Cocoa Touch, even if I don't follow them completely, I'll be able to get more out of the other tutorials I find online. I'll have better context for them.
Practice, practice, practice.