My new Intel iMac is coming in the mail in a day or two, and I'd really like to learn how to program software for OS X and for my iPod Touch. Where can I learn how to do this? So, as the question says, I'm getting a new Mac and I'm really interested in learning to write programs for it. I also got an iPod Touch free with the Mac, and I want to learn how to use the SDK to write programs for it. What resource can I use to learn this? Obviously, a free internet source would be great, but I'll buy a book if it's really good and will help.

I know C++, C#, and by extension a fair amount of C. Definitely willing to learn a new language to do this; I'm just not sure where to start.

So, AskMeFi, what's the definitive source for programming OS X?