I'm starting some mac development. I'm reading "Programming in Objective-C" by Stephen Kochan. I also have "Cocoa Applications" by Simson Garfinkel & Michael Mahoney.
One way I justified buying a Mac Mini for Jane was the possibility of being able to do Mac development on it. It comes with all the development tools necessary. So hear I am.
I'll keep a log of my experience as a first time developer on OS X and post the most interesting comments on my blog.