My wife and child are in San Antonio for the weekend, so I'm left alone to — what else? — write code! I have embarked on a 36-hour code jam with Objective-C and Cocoa. I'm attempting to build a personal finance application for my own use that may turn into something more.
If you want to write apps for OS X and you'd like to be productive in a hurry, I super highly recommend watching this video tutorial from Apple that demonstrates building an application with a technology called Core Data. Core Data was introduced with Tiger (aka OS X 10.4) and is just monstrously useful. With the information in the tutorial alone, you can write a zillion simple, handy apps.