Beginning Mac Programming: Develop with Objective-C and Cocoa (Pragmatic Programmers)
Tim Istedhas been writing software for Macintosh computers since 1995. He also builds Web applications using Ruby on Rails, PHP, and .NET, and has been known to develop for Windows machines, too. He blogs on Core Data at www.timisted.net, and is currently co-organizing NSConference, a conference for Mac developers.