A First Look at Objective-C - Article by Noah Roberts.
ActiveDeveloper - Interactive runtime Objective-C IDE for Windows, Mac OS X, OpenStep NIS.
Cetus Links - Objective-C - Links on Objects, Components and Objective-C. Provides links on tutorial, newsletter, books, software and libraries.
Cocoa - Apple's Objective-C based Cocoa programming environment for Mac OS X.
comp.lang.objective-c FAQ - Frequently asked questions about Objective-C.
distcc - A gcc wrapper that speeds compilation by transparently distributing work across several machines. [Open source, GPL]
G++ FAQ - A list of frequently asked questions (FAQ) for g++ users.
GCC - The GNU Compiler Collection - GCC was developed by GNU to provide a free compiler for the GNU system.
GCC XML Node Introspector Project - Project to create an XML interface to the GCC AST tree_nodes and store in Postgres Database.
GCC6809 - GCC for the Motorola 6809.
GNU Development Environment - Suite of GNU C/C++, Fortran, Java Cross Compilers, and Insight/GDB Debugger hosted on Windows NT/2K/XP for embedded ARM7, ARM9, and XScale CPU applications development. Includes Assembler, Compilers, Linker, Header Files, STL, Libraries, and Documentation.
GNU Fortran for OS/2, DOS and Win32 - Port of GNU Fortran (g77-0.5.23) for EMX (OS/2 and DOS) and RSX (Win32 console-apps, DOS-DPMI).
GNU Objective-C runtime features - Some notes about garbage collection and type information strings in the GNU Objective-C runtime (2.95.3 GCC version).
GNUstep - A GNU project to write a completely OpenStep compatible programming environment based on Objective-C, with intentions to also maintain Mac OS X compatibility.
MinGW (Minimalist GNU for Windows) - GCC Win32 port. GCC, GDB and binutils ports for building native Win32 programs that do not rely on any 3rd-party DLLs.
Object-Oriented Programming and the Objective-C Language - A full-fledged manual to the Objective-C language extension.
Objective-C Resources - Directory Objective-C resources.
OpenStep Specification - A copy of NeXT Computer's OpenStep Specification. This is the specification that both Cocoa and GNUstep are based on.
Optimizing Objective-C Code - Articles and samples to help you get maximum performance from your Objective-C code.
Portable Object Compiler - A preprocessor that will convert Objective-C into regular C.
Programming in Objective-C - Some introductory notes and examples of Objective-C.
Programming: Objective-C - Includes tutorials, reference material and downloads.
RHIDE - A free IDE by Robert Hoehne and Salvador Eduardo Tropea for DJGPP. It runs on DOS and Linux and looks just like Borland's old DOS IDE. It has project management, a frontend to GCC C/C++ syntax highlighting and an integrated debugger.
Sample Objective-C Source Code - Tutorials and examples including hello world, stacks and queues.
Shakespeare Programming Language Frontend - GCC frontend for a small beautiful language, which resembles the Shakespearian plays.
Steve Dekorte's Objective-C page - Overview, language comparisons, history, compilers (platform chart and feature chart), project links.
The MiscKit Frameworks - A free collection of Objective-C objects useful to Rhapsody, OPENSTEP, GNUstep, and NeXTSTEP programmers.