Where can the System-Provided Buttons and Icons mentioned in the following link to the iPhone Developer Human Interface Guidelines be found in the SDK? http://developer.apple.com/iphone/library/documentation/UserExperience/Conceptual/MobileHIG/SystemProvided/SystemProvided.html
I expected them to show up in Interface Builder somewhere, but I haven't been able to locate them.
Reading that link pointed me to this page, which under the appearance heading (as directed) I found the following quote:
In addition to custom buttons, you can configure bar button items using several standard images and titles. When a bar button item is selected, the Identifier field of the Attributes inspector lists the type of the button. Choosing a type other than Custom lets you create buttons representing standard system actions.
I believe this is the link you want (you must login to the developer site to get it)... http://developer.apple.com/iphone/library/documentation/UserExperience/Conceptual/MobileHIG/SystemProvided/SystemProvided.html