Odd how I'm reading up on all things Mac related but I really do want one! So when the time does come and I get a iMac/iBook/Powerbook (note the order of affordability there!) then I could jump right in and get my feet wet.
Apple has been rather clever by including a complete development environment with every copy of MacOS X. This way they are encouraging people to develop and increase the number of applications that are available. Now Microsoft feels that you should shell out quite a bit for Visual Studio.net although it seems that they are changing their minds especially with the Visual Studio Express products that are now in beta form.
Anyway browse on over to Maczealots and check our some of the articles there. The one about development is available here and should get you up to speed in no time.
So now to start learning C ... sigh!