Now, for the iPhone, we can't use Class-Dump, because it doesn't recognize binaries compiled for the ARM6 processor. Additionally, we shouldn't use it, because it means we're poking around in private stuff that could get our Application banned from the App Store.
But, for the curious, I thought I'd point out that you can actually use Class-Dump on iPhone frameworks; you just have to run it on the framework that's in the SDK for the simulator rather than the device. The iPhone simulator is NOT an emulator.. it's not running ARM6 byte codes, it's running X86 byte codes (except for those naughty people who installed the SDK on a PPC Mac).
So, want to see the headers from the UIKit in all their glory?
class-dump UIKit > ~/Desktop/UIKit.txt
But, shhhh.... You didn't learn it from me.