MGTwitterEngine
MGTwitterEngine is a Objective-C class which lets you integrate Twitter support into your Cocoa application, by making use of the Twitter API. The entire API is covered, and appropriate data is returned as simple native Cocoa objects (NSArrays, NSDictionarys, NSStrings, NSDates and so on), for very easy integration into your own application. MGTwitterEngine is designed for Leopard, but should be just fine on Tiger too.