Dr. Dobb's - The Fifth Column
Good general resource including Michael Swaine's subversive perspective on the world of Macintosh development updated each month. Offers source code, online search, and book reviews.

GNUstep Project
A project devoted to providing an object oriented application framework to developers.

iDevGames
Macintosh game development website featuring news, tutorials, game assets, forums and articles.

Mac OS 8 and 9 Developer Documentation
Gateway to Apple's documentation for programming Mac OS 8 and 9, including Carbon development.

Macdev at MIT
Various resources for Macintosh development from the folks over at MIT.

MacHack
"The Annual Conference for Leading Edge Developers"; a multi-day round-the-clock ritual involving gallons of soda, heinous hacks, and lots of camaraderie. Not to be missed!

MacOS Web Directory
A directory of Mac programming related sites, including development kits, format specs, toolkits, open source, tutorials, and webzines.

Sound & Vision, Inc.
Develop software for Macintosh platform. On this site users can find information about FineReader 5 Pro, development and layout software.