I'd like to learn how to write application for Mac OS X.
Like how to use XCode properly, Cocoa syntaxes and examples, etc.
I'm already a web developer using ruby, php, mysql, rails, etc.
I looked through google quite some times but never found something palpable to learn from.
But I really want to make my own application, for fun and maybe business later.
Thanks a whole bunch for your tips!
To jump right in as quickly as possible, I'd recommend going through the following Cocoa Dev Central tutorials:
Once you've read those, you should be able to do quite a bit on your own, just using the documentation in Xcode (option-double-click on a class name in Xcode) and Apple's developer site.