Macintosh Application Development Essentials (MADE
a tiny package of C/C++ code which provides all the lowest-level needs for a Macintosh application. It is designed for people who are learning, or know how to program Macs, but don't have the time, energy or desire to write basic menu, event, memory and error handling routines.
MacZoop - the free C++ application framework for M
The free framework to use for all small-to-medium sized projects and if you're a newbie. The MacZoop website has everything you need to get started.
Whisper
a general purpose Mac/Win32 C++ application framework. It's the successor to the Mac framework Raven. Offers development status, statistics, notes, and downloads.