Finding interesting stuff for the Mac is difficult given the relative numbers of users and programmers out there. I think I may have found something though.
In the *NIX world (including OS X) the Python language seems to be the up and coming thing for programming. Python is an interpreted object oriented language. Python comes free with OS X, Linux, and BSD. It has to be downloaded and installed if it is to run on a Windows machine. I have tried simple GUI programming under Linux and will try it for the Mac as I get to that point.
The book itself contains a number of exercises as well as instructions on how to write programs in Python. I have only reached the second set of exercises but have already found a number of useful items. Those starting out may want to take a look at my recent articles on shells and shell programming. Although it is possible to program exclusively in a GUI environment, it is still a very good idea to start out using the shell then transition to the GUI.
The title of the book is “Learning Python The Hard Way“. The link to the authors web site is http://sheddingbikes.com/posts/1285754959.html. Please read the information on the page before downloading the book.