I just stumbled upon 10 Mac freeware applications I think are very useful, like:

iAlarm allows users to control how they wake up in the morning by leveraging the power of OS X. iAlarm provides 7 basic alert types for users; play iTunes, speak the headline news, speak a custom message, speak your daily events and to do items from your iCal calendar, speak the local weather, and of course a standard beep.

MGTwitterEngine is a 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 Cocoa objects (NSArrays, NSDictionarys, NSStrings, NSDates and so on), for very easy integration with your code.