Apple offers the SDK for free download - but from what I can tell, if you want to watch the Getting Started videos, read How-To's or download their sample code, you have to sign up for the $99/yr developer program?
I'd like to tinker around a bit and learn how to write programs for the iPhone, but have no interest in testing on an actual iPhone or distributing a program though the App Store. Is there a way for me to save having to spend a hundred bucks just to play around?