I recommend checking out Stanfords CS193p courses. Here's a link to their videos in iTunes. You'll need to search around to find the documents for homework. The lectures help a lot in understanding Objective-C.
http://itunes.apple.com/us/podcast/cs193p-student-final-proj...Also become familiar with Apple's iOS Dev Center. If you're going to do iOS development than you will need to know your way around this site. http://developer.apple.com/devcenter/ios/index.action
Finally the Head First series of books are really good especially if you feel like you are a novice. They have a book for iPhone and iPad development. http://www.headfirstlabs.com/books/hfiphonedev/