Recently, I need to start iPhone App programming in the project I am working.
Here are some useful references for beginners.
[Books]
1) Dave Mark and Jeff LaMarche, "Beginning iPhong Development", Apress, 2009.
2) Erica Sadun, "The iPhone Developer's Cookbook", Addison-Wesley, 2008.
3) "Learn Objective-C on the Mac", 2009.
[e-Books]
1) Bert Altenberg, Alex Clarke and Philippe Mougin, "Becom an Xcoder", 2008.
2) "Learn Objective-C 2.0 Language"
[Webpages]
1) Apple's iPhone Dev Center
2) Stanford University, CS 193P "iPhone Application Programming"
3) CocoaLab
4) Jeff LaMarche's iPhone Programming Blog