Debugging
BugLink, CoverTest, Develop Articles on Testing and Debugging, Mac Tech: Getting Results With Macsbug, MacNosy, Macsbug, Secrets of the Debug Meisters, TestTrack and SoloBug, The Debugger, The Memory Mine
Languages
BASIC, C and C++, Card-Based, FreeCard, HyperCard, Java, MetaCard, Pascal, Perl, Python
Libraries
3D, Database, Frameworks, OpenGL, QuickTime, Text Engines, FAXstf Developer's Kit, GameCode, Internet Config, Macintosh source archive, Mercutio MDEF, PIconServices, Piddle Backend, Programming Utilities, Sailmaker Software Limited, Sound Core
Mac OS X
AltiVec Programming, Apple Developer Connection: Mac OS X, Big Nerd Ranch, Cocoa Dev Central, CocoaDev, Mac OS X Programming: Getting Started, O'Reilly MacDevCenter, OmniGroup Source Code and Frameworks, Perlidex 1.1, Programming on Mac OS X.
Open Source
Apple - Open Source, High Performance Computing using Mac OS X, Mac OS Open Source Software Directory
Porting
MacLame, MicroAPL Porting Tools and Services, SkyeyTech, Vertical Solutions, YAAF - Yet Another Application Framework
Reference
Develop - The Apple Technical Journal, Gestalt Selectors List, How to Program Your Mac, Quinn's Human Interface Subtleties, Quinn's Newbie Mac Programmer Hints, ResExcellence, The MOST, Thomas Tempelmann's Mac Developer site, USENET Macintosh Programmer's Guide
Sources
CodeSourcery, LLC, Hsoi's Shop, iDevGames.com, Ingemar's Corner, Kyle Hammond's Mac Programming Page, SourceForge
Tools
Assembly, Database, Open Source, Version Control, Apple Development Tools, AppMaker, BBEdit, CodeBuilder, CodeWarrior, Cygnus Solutions FTP directory, Developer Depot, Excel Software, General Edit, Guide to Think Pascal 4.5d4
Apple Developer Connection
Provides news and technical information for Apple Developers.
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.