Step into Xcode
Picked this up today from the local Uni bookstore (Hurray for student discount!) to aid in fleshing out the Cocoa client, which may be a 0.0.4 release if I hack something basic together, or 0.1 if I’m happy with the basic feature set.
Anyway I’m only a few chapters in, but have learnt more about Xcode in an afternoon than in the last couple of months. Great reading, and I highly recommend picking up a copy if you want to do any kind of OS X development.